THE DOCTOR

We're running again. Always running – sometimes towards things, sometimes away from them. Sometimes for our lives. Today we are running for our lives. We think we are, anyway. We don't want to find out.

'Run!' Jack yells, from just ahead of me. We are already running, Martha and I. I can hear her breath starting to come in wheezing gasps, even above the thudding of my own hearts. We can't yet hear the footsteps of our pursuers, but then, you can't hear footsteps when the feet are running not on solid ground but on a solid-barrier forcefield. Everything around here is forcefields.

Martha's s hand feels small in mine, and I'm probably hurting her fingers with the strength of my grip. I tighten my hold on her anyway, and I'm pulling her along.

The corridor is long and straight – like all the others – and a uniform sterile grey-blue. There's nowhere to hide or take cover – but suddenly Jack bounces off nothing as if he's run into a brick wall, and I only have time to slow my pace slightly before my leading foot strikes an invisible barrier and I am knocked over, clattering Martha to the floor with me.

I'm panting and feeling the tingle of an adrenaline wash, as we grope our way upright. My sonic is in my hand before I've even thought about it, and it's the work of moments to discover the correct resonating frequency of the forcefield and disrupt it. As it flickers into visibility and instability, I push Martha through first and Jack is right behind me.

Three more invisible barriers later, we are bruised and scared. They seem to switch on just as we reach them. I've never come across a race before that builds using forcefields rather than solid materials. The sheer power required is astronomical, and it was the extraordinary and dangerous levels of power generation on the planet's surface that had drawn us to materialise the TARDIS here in the first place. Now, the forcefields are changing the layout of the base itself, even as we run, and it's only a matter of time before we are too slow.

As we pile through the lastest sonic-disrupted invisible wall, I find myself wondering whether our pursuers are playing with us. They seem to know exactly where we have got to, and exactly where to flick the next barrier into existence.

We are still running when they seem to tire of their game, and they're suddenly close behind, horribly close, and I almost regret not letting Jack bring his blaster. I'm looking over my shoulder at the grey-clad security detail – six of them, armed with what look horribly like some kind of laser disruptors - as the first white-hot explosion rips through me.

My shoulder is on fire, and everything turns grey for a moment. Through the ringing in my ears, I think I hear another explosion, even closer, and I use the last of my strength to drag Martha down with me, out of the line of fire.

As we fall, we collide with another barrier, and ricochet to the left in a tangle of limbs. My face is pressed into Martha's leather jacket – I've landed on top of her, and she isn't moving. I can't seem to make my right arm work properly to prise myself off. I try again and cry out in agony through clenched teeth, swallowing back a surge of bile. Rassilon, this hurts.

It's only a moment before I'm dragged upwards and pressed against the barrier. My right arm is hanging uselessly, and the whole of my shoulder and half my back feels like it's been blown apart. The world is fading in and out of focus and I'm not sure if it's the injury, or the lack of oxygen – the hand that's pinning me to the barrier is round my throat.

There's a jumble of words, sounding like an accusation, but they don't seem to make sense. I try and speak but there's an awful gasping choking sound instead. My respiratory bypass allows me to survive for a while without breathing, but I can't do anything about the strong hands crushing the main arteries in my neck. There's a roaring in my ears, and a throbbing heat across my eyes and temples, as the hand presses harder – the voice seems insistent and accusatory, but I'm beyond hearing it.

I persuade my eyes to flick downwards to check on my companions. Jack is dead again. There's a big smouldering hole where the left side of his chest should be. Martha is on the floor, and she isn't moving. My last thought as the world narrows to a tunnel of throbbing lights is that I hope she only hit her head as I dragged her down. Then there's only darkness.

...

Pain. Nausea. White light hurting my eyes. Keep them shut. Breathe. Breathe.

Then I remember. No wonder my shoulder's in agony, and my whole body feels like I've been beaten. Laser disruptors: one of my many least favourite weapons. They keep on destroying, like an expanding bullet – no, it's slower, more like gangrene starting from a wound and eating away at the whole body. It's agony, and I'm slightly surprised I've not regenerated. There's still a chance it might come to that.

Martha and Jack. Rasillon, I hope they're OK. Jack was dead. I hope they disposed of the body somewhere that will let him escape. But Martha? I think the pain in my gut might be guilt, and I'm almost physically sick with worry about what they might be doing to her.

It says something for the state of my body that I've not moved yet, but I know I have to. For one thing, I need to sort out my shoulder. I don't have to open my eyes to know that I'm lying in a pool of my own blood; I can feel it draining out, and I can smell it. I open my eyes anyway, and risk a glance down. It's actually worse than I feared. I don't know if the initial disruptor hit was strong enough to rip all the way through my body, but the ongoing cellular decay has made a substantial cavity, and there's blood pooling in it, overflowing enough to seep through and drip onto the floor. I must have been unconscious for a while for it to get this bad. Again, I'm surprised that I've not regenerated. Yet.

I try and roll onto my left side, so that I can sit up. The pain spikes badly enough to make me choke back bile and swallow a sob. I try again. And again. Fourth time, I'm shaking with exhaustion, but I'm there. My head is drooping, but my left arm is holding firm, elbow locked, as I finally get my legs to co-operate and begin to crawl.

Of course, it's a forcefield-constructed cell I'm in, too. Bright white opaque walls, floor and ceiling, and no visible corners at all. It takes me a whole minute to reach the nearest vertical wall and rest with my back against it. I close my eyes and just breathe for another minute, and when I open them a crack I can see a trail of vivid dark red. It's offensive against the stark, oppressive white of everything else.

My hearts must be working overtime to keep what blood I have left circulating, because most of it seems to be on the floor.

I'm cold, and the shaking isn't just from exertion, it's the shock of pain and blood loss, and the continuing slow decay of my body spreading from the disruptor wound. I persuade my left arm to move, and it takes far too long to reach the sonic in my inside pocket. My fingers are clumsy and it's hard to find the right setting. I know exactly how to stop the disruptor's insidious work, but that doesn't mean I want to do it. Wishing fruitlessly for one of the painkillers I keep in the TARDIS medical room, but hardly ever use, I try not to think too much as I press the tip of the sonic right into the centre of the wound, and thumb the switch before the pain can knock me out.

The familiar whine of the device is drowned by my own screaming, and I'm not even sure I'm keeping the sonic aimed in the right place because my whole body is wracked by spasms from the agony of what I'm doing. It seems to take for ever, but when I finally drop the sonic and stop screaming long enough to breathe, I gag at the smell of cauterised flesh, and loose what little was in my stomach. The vomit joins the blood to stain my clothes, but I'm in too much pain and too exhausted to feel disgusted.

Now I've stopped the decay, I want nothing more than to sink into a healing coma, and wake up when I can function again. But even a being as physically robust as a Time Lord can't heal this kind of injury in an hour or two, and I can't abandon Martha. I don't even know whether I'll be able to escape, but it's not in my nature not to try.

I hold the sonic between my teeth, and use my left hand to loosen and then remove my tie. A few moments later my useless right arm is supported in a make-shift sling. I stay leaning against the white wall, and still myself so I can start to analyse the frequencies. Carefully, I change the sonic's setting to something less painful, and aim it over my left shoulder, directly at the wall, eyes closed so that I can concentrate only on the sounds. If I can resonate at the same frequency as the forcefield, then I might just be able to create a feedback loop that would short out the field generator for long enough to let me through. I try to banish the mental image of what would happen if the forcefield were to recalibrate itself and click back on when I was half way through.

It takes me two minutes – one minute and fifty-five seconds longer than it should – to realise that the forcefield is operating on a randomly modulating frequency, and that therefore I have not a chance of keeping up with it. I am stuck here until they come for me, or until Jack resurrects and works out how to knock out the forcefields at their source.

JACK

There's a very brief moment when I know I'm about to die again, but before the pain hits and is replaced by the nothingness of death. I use that moment to hope that the Doctor isn't as badly injured as it looks, and that I can come back to life in time to stop them hurting Martha. There isn't time to think anything else. There isn't even time to scream.

...

My lungs are burning, but I hold in the urge to take a gasping breath. Long experience has allowed me to exert some control over the nature of my resurrection. In and out. Through the nose. Nice and steady til my heartrate dips under 200 beats per minute and I stop feeling like I'm about to die all over again. It doesn't help that I can feel the last bits of the gaping chest wound still knitting themselves together. Breathe. In and out. Nice and slow.

As I breathe as silently as I can, I listen, but there's nothing but a humming noise, so I risk opening my eyes a crack. Now I know why there is such a God-awful smell. I wish I wasn't on a rubbish heap, but it says something about my life that I'm grateful that whoever it is that runs this facility is thoughtful enough to separate organic waste from effluence. Even if the effluence is only in the next container along. In fact, for a waste disposal room it's incredibly ordered and tidy.

I've seen, heard and smelt enough, and before I add vomit to the already-disgusting pile that I'm lying on, my heartrate is down to a level that will let me safely sit up and start to explore the possibilities for escape. I stretch, cracking the joints and enjoying the feeling of being alive. That never fades. It hurts like hell to die, and it's almost worse coming back to life again, but that feeling of simply being alive? There's no adrenaline rush in the world that can beat it.

I jump down from container – I really don't want to call it a compost heap – and head for the door. There's something to be said for being dumped in the waste and recycling bay. Nobody, no matter how paranoid they are, expects their trash to try and escape. It's all forcefields again, of course – walls, floor, ceiling, doors. What's wrong with these people that they don't want to build out of actual matter? The main door doesn't even locking system from the inside – there's an emergency release button to the right of it, and it's even labelled in red. When I'm through the door, the corridor is deserted. I make a bet with myself about how long it's going to take me to locate the main power generator – or at least the main power conduit, if the generator is too far away. I like to think it will be less than an hour.

It's actually only around forty minutes later that I find what I'm looking for. The main power distribution nodes take up a whole room. I have to admit I'm in awe. This is a colossal amount of power. The Doctor had talked about some pretty big numbers when we first picked up the readings, but it's another thing to see it in action. And the set-up is state of the art, each node almost completely silent, but there's so many of them that the hum in here is loud enough to be borderline painful. They've got the whole area mapped out in four dimensions, and every single forcefield – floor, wall ceiling, door, even the cupboards – are powered through this room. It's too bad about the twelve security personnel who are monitoring the whole thing, and about the fact that they're standing between me and any chance of cutting the power and getting the Doctor and Martha out of here. It's also too bad that everything seems to be controlled by telepsychic projectors on the guards' helmets. That's not something I'll be able to pick up and do myself (though the Doctor probably could).

I'm not armed – when am I ever these days? – but if I creep back to the garbage room I might find something I can salvage to help me past the guards. I remember a small container of waste metal, and I'm the sort of guy who can give almost anything a new and violent purpose – I expect that's what the Doctor thinks of me anyway. Well, maybe this time it's in his interest that I probably can. For a moment I wonder whether the simplest thing might be just to barge in and hope for the best – there's only a very remote possibility that I might succeed on the first attempt, but even if I die in the attempt, I'll probably end up back where I want to be anyway – with the garbage.

I decide to take the less painful route; it wasn't much fun dying from a laser disruptor hit earlier on today, and I'm not in a hurry to try it again. I'm getting worried about the time it's all taking to effect some kind of rescue, but considering they've had a fairly serious security breach today, there doesn't seem to be the sense of underlying emergency that you'd expect. In fact, everything seems extraordinarily calm and ordered. I think this probably bodes well, so I'm not wasting any more time.

Actually it's eerily quiet. I think I almost prefer being shot at - you know where you are when you're being chased and shot at by armed guards. Maybe they're just very confident, and they do have a point – the trick with moving the invisible walls was a good one.

But I'm back at the garbage area without incident, and it really doesn't take me long to find what I'm looking for: something sharp enough to cut through cable insulation (it looks like a sheared-off piece of trilinium from an engine casing), two canisters of some sort that look like they could be re-sealed, together with some conductive wire. I can get everything else from the compost bin – the first thing I'm going to do when we get back to the TARDIS is have a shower and a change of clothes. I've spent far too much time today communing with rotting waste.

But I've got what I need, and it's only five minutes' work to turn this small pile of junk into a something that will go with a bang. I am in my element, and I have to keep reminding myself that I'm not supposed to be having fun. Thinking of the Doctor's gaping, smouldering shoulder wound helps keep me focused.

I waste no time, and head back to the power distribution nodes, settling myself out of sight, and holding the conductive wire (now connected to one of my canisters) between my teeth. Each canister is filled with a different combination of rotting matter, and all I need to do to enact phase one of my plan is ignite the first canister with a burst of power from my vortex manipulator. The fuse is made of what looks like someone's hair, or possibly fur, rubbed in oil scraped off some of the scrap metal. It lights first time and I roll it gently towards the group of security guards. By the time they hear it, and turn round to investigate the noise, it will be too late.

Call me Captain Perfect Timing. No, really do. The gas that's escaping from this little beauty is enough to knock out a mammoth, and if they shoot it, all that will happen is that the explosion will conveniently distribute the base chemical all over them.

Yep, they've shot it. I knew they would, so I've already got my eyes shut and I'm breathing through my compost-encrusted sleeve, though the gas won't have much effect on me anyway. I smile at the happy thud-thud of bodies hitting the floor (and I even feel proud of myself that they're not even dead, just unconscious), before quickly relieving the guards of their weapons and stashing them against the bank of nodes.

There's a moment of panic when I'm not sure which of these I'll need to take out (it's not helped by the way my eyes are watering from my little gas-bomb) – I don't want to cut out the environmental controls, or the outer shell of the base, just the internal construction. There are literally thousands of individual nodes, but there are only three main power routers serving the whole lot of them. There are icons on each note control, and I take a guess as to which bank is the one I want. This is where my handy piece of scrap trilinium comes in, allowing me to cut through most of the insulation and thread my own conductive wires in parallel. If I've got this just right, I can take out just the internal forcefields relatively safely. That's the theory, anyway. I kinda wish it was the Doctor doing this bit and I was still dead somewhere, actually, because if I get this wrong it could be spectacularly wrong.

No time to waste. I unroll the rest of my wire, and ignite the second canister that I've connected to it, retreating to what should be a safe distance.

...

MARTHA

Waking and finding yourself tied up is horrible; even when it's happened before, you don't get used to it.

God, my head hurts, and I can feel every bruise down my back. I think they are mostly from where the Doctor fell on me. Hope he's alright. I don't think I am. My head's throbbing, and there are people (sort of people, anyway) with nasty looking guns pointing at me. The Doctor's brilliant at getting out of these situations, but I don't even know where he is.

They ask me stuff – a whole bunch of questions about what we're doing here – but as usual we've just blundered in with no plan, and there's nothing I can tell them even if I wanted to. I realise all over again how little I really understand of what we actually do when we travel with the Doctor – we just seem to run from one crisis to another. Sometimes I wonder if we create the crises merely by arriving.

I try a bit of Doctorish negotiation, and even a bit of friendliness, but it seems that's not really their style. I don't know if it will be worse if they realise I don't know anything or if they carry on thinking that I'm hiding something. It doesn't start too badly, not at first. They just shout and wave their weapons – if they weren't the ones holding the guns, I'd say they looked scared, but that's can't be right. I babble something useless about just being a passenger and not knowing anything. I'm terrified, but I keep thinking that I've been in worse situations than this and the Doctor has always got us out of it. But he's taking his time. If he's even OK at all. And Jack, too. I could really use one of them sauntering in and rescuing me right now. I don't really mind which of them it is.

OK, now it's bad, and now would be a good time for that rescue. There's two of them behind me and I can feel their breath as one of them forces my head to the side to expose my neck. When I struggle it just hurts more, and there's nothing I can do to stop them administering a hypospray of some kind.

Bloody hell, whatever it is it's fast acting – almost as fast as the sleep patch I was given when I was carjacked on New Earth. It's only a few seconds before I'm struggling to breathe. There's a ghastly gurgling rasping sound, and I realise with horror that it's me. My throat is on fire, and it feels like I've got something stuck in there.

I'm suffocating, and my eyes are burning, and I can't help thrashing in the chair. From the reaction of the guards this wasn't supposed to happen, and their own panic would be almost comical if they hadn't just pretty much killed me. I'm barely aware when my head is grasped again and there's a second sting in my neck, and my arms are abruptly released from the straps.

That's when all hell really starts to break loose.

...

THE DOCTOR

I must have drifted off for a bit there. But there's no point feeling woozy if it doesn't even take any of the pain away. I have no desire to move. Ever again. If Jack comes to rescue me I might have to move. I might even have to run. That could be difficult. Actually, it could be impossible. I've been sitting here completely still for a while now, doing absolutely nothing, but I'm actually out of breath. It's been a while since I lost this much blood all at once. Probably not since I was last shot, and I ended up regenerating that time. Hmm. Breathe. In. Out. In. Out.

I wonder whether Jack will find the main power distribution centre. I wonder if he'll work out not to cut the power to the internal forcefield that's trapping me without first making sure that the artificial gravity will stay on? Maybe he didn't notice the gravity was artificial? Maybe he won't even think to isolate the internal and external forcefields. He wouldn't just blow the whole generator up, would he? This is Jack we're talking about, though. That would be a quick way to suck us all out into what looked from the TARDIS' analysis to be a fairly hostile atmosphere.

Then again, maybe Jack's still dead. Or worse. Maybe they kept the body, and have discovered his little secret. That wouldn't be good. The sensation of guilty worry surges in my gut again, and I swallow it down.

When it finally happens there's no warning. One moment I'm letting my eyes drift shut against the glaring white and red of the cell, and the next it's all darkness and chaos, and I'm falling what used to be sideways, but must now be down. My last even vaguely coherent thought is that I wish Jack had worked out about the artificial gravity, then it's all just pain again – I'm falling, and I catch my foot on something which sends me spinning, and then there's a blow to my lower back that knocks all the air from my lungs. The next blow catches the side of my head, and I'm almost glad that I'll probably be unconscious before I finally hit the floor.

...

JACK

The initial explosion is a little disappointing. Actually, it wasn't supposed to be a really big bang, just enough to take out the main power cable to the internal forcefields, but I've miscalculated, because everything is suddenly dark, and the pillar I was leaning against has disappeared. I'm falling sideways, and there's nothing to grab hold of because I've just switched everything off and nothing is solid here. I curse aloud my own stupidity. It's a long fall, and there's time for a lot of swearing before I finally hit the all-too solid ground with a crunching noise that would have turned my stomach if there'd been time before I die for the second time in as many hours.

...

MARTHA

I can still barely breathe, I can feel my heart thudding frantically, and I hurt all over, when without warning all the lights go out, and the bottom drops out of the world. As I fall sideways, there's shouting, and it seems that my captors are as surprised as I am. Instinctively I cover my head with my arms, but it's not a long fall, and it's broken by something relatively soft, which might be a person. Whatever it is it isn't moving. For a minute I just lie there, sucking in as much air as I can through my still-constricted throat, and blink back stinging tears in the suffocating dark.

JACK

It's still dark when I jerk back to life. I ache all over, so I'm kinda glad I died – recovering from that many broken bones would have been hell to live through, even at my rate of healing. The darkness is full of the heavy scent of disaster, but it's the sound of ragged breathing that I end up following, as I pick my way through debris by the minimal light of my wrist-strap display. Every so often there's a hitching sob, and I don't know whether to hope it's Martha or the Doctor, or some suffering stranger.

It is Martha, and it only takes me a minute or two to find her. She's curled up in a foetal position, and I can't see much of her face because she's got her arms wrapped round her head as if they can protect her.

'Martha?' I crouch down beside her, speaking softly. My knees crack painfully and I have to steady myself with a hand. I don't want to startle her; I don't know what she's been through. I also don't want to attract the attention of anyone else who's made it through my little power cut.

She uncurls just a fraction, and there's a minute pause in the rhythm of her laboured breathing, then she's up and almost knocking me over, arms round my neck and she's trying to say my name but her voice is reduced to a croaking gasp. God, what have they done to her? I enfold her small frame in my arms, and rub circles on her back to try and calm her breathing. She's like a frightened bird.

Eventually, I speak softly into her hair. 'We need to find the Doctor.' She nods into my shoulder, and doesn't try to speak. I think she knows she can't at the moment. But she's almost steady on her feet when I've pulled her upright, though her breathing still doesn't sound good.

We find the TARDIS first. Like everything else, it fell when the gravity failed, but landed, cat-like, the right way up. Light streams from the doors when we open them, illuminating a scene of devastation. Bile rises in my throat at the sight of the bodies. I did this. I don't even know if they're dead or just injured. These people killed me, but I still hate myself. There was a time when I wouldn't have cared.

I leave Martha in the TARDIS. She's coughing and wheezing, her face looks swollen and blotchy, and her pulse is racing. I tell her to go find some oxygen in the medbay while I go out to try and look for the Doctor.

The time ship's light proves to be just enough, but when I find him the Time Lord looks like just one more body, still as death, as he lies crumpled in a pile of debris. I thrust my fingers into the fold of his jacket to find a pulse, and release a breath I didn't know I was holding. He's alive. It takes me a while to dig him out, and all the time I want him to spring up, all smiles and energy, or even all disappointment. He doesn't even groan. There's blood on the side of his face, and his right shoulder is a mess. I'm not sure why he hasn't regenerated. He looks worse than a corpse.

You shouldn't move people who've fallen from a height. But there are sounds of stirring behind me, and I have no choice but to pick his bloodied body up and carry him back to the TARDIS before any of the natives rouse themselves enough to pick a fight. I try not to step on anything that looks like it might be still alive. I try not to think about what the Doctor will say when he realises what I've done to try and save him.

THE DOCTOR

Rasillon, everything still hurts. Couldn't I stay unconscious long enough for the worst of it to be over? I can't seem to open my eyes, but I know it's Jack standing over me. His nearness is like an open wound in the fabric of everything. But I'm still glad he's here.

'Doctor,' he says, and I get the impression it's not the first time he's called my name, trying to rouse me.

I speak his own name back to him, without opening my eyes. My voice sounds scratchy and weak even to my own ears.

'Doc, I don't know what to do,' he's saying. There's controlled panic in his voice; he thinks I'm dying. Maybe I am. But he sounds so lost, and I find myself wanting to make an effort for him. I crack my eyelids open, and they find his blue eyes. He's as alive as ever, the impossible man, but he's covered in blood, and he stinks of something I can't identify. It almost masks the scent of the TARDIS' medbay.

What I really need is a day in the zero room, but I need to let Jack or Martha do a bit of first aid before I sink into a healing coma. My body is pretty good at knitting itself back together in the right order, but I fear it may struggle to put the bones in my shoulder back correctly without a bit of medical intervention.

With some effort, I turn my head to the side, looking for Martha. She's there, but my eyes widen when I see her, perched on one of the stools and leaning heavily against the counter, an oxygen mask pressed to her face with one hand, and the other hand supporting her forehead.

'Martha,' I manage, weakly, and her head snaps up straight away.

She quickly unfolds herself from the stool and a moment later she's standing beside me, and reaching to hold my left hand. I'm alert enough to grasp her wrist, and to work out from her appearance and her racing heart-rate what's likely to have happened. At least she's alive. They must have given her an epinephrine equivalent to counteract the reaction to whatever toxic substance they'd pumped into her. I feel my face heat in anger and protectiveness, and I manage to gasp out the name of a drug that will help her, together with its appearance and location in the TARDIS' extensive medical stores. She nods, and I close my eyes in relief, letting go of her wrist so that she can fetch the medication.

MARTHA

I dose myself with whatever it is that the Doctor suggested, and immediately I can feel my heart returning to normal and my throat is less constricted. Jack's asking whether I'm sure the drug was for me rather than for the Time Lord – but I know the Doctor, he would always think of our needs first, before his own.

At least now I am well enough to help him. I know all he wants to do is sink into one of his scary healing sleeps, but I want to check the damage myself first.

The shoulder wound is the most obvious, and I start to peel back the singed fabric of his jacket and shirt. I've never seen anything like it. The flesh is part burned, part eaten away, and I can see right through to the smashed bones in places. How is the man not screaming? Maybe he's beyond it.

Before I do anything else, I quickly fetch a hypospray of the painkillers that he never bothers to use, and discharge the full strength through the skin over the main artery in his neck. The tension that I'd not even registered was there suddenly relaxes, and his eyes flutter open briefly.

'You're welcome,' I say, and then set about hurting him even more as I try to make sense of the mess of bones, ligaments, nerves and blood vessels that used to be his shoulder. Jack is giving him the oxygen that I was using before.

It's reassuring when he groans in pain. It shows that the nerve damage isn't as catastrophic as I feared, and by some miracle, there's still a functional blood supply to the right arm. There's not much I can do for him, except stitch the worst of it back together, keep it covered, and hope his own unique physiology can do the rest.

The rest of his wounds are serious but not life-threatening. The head injury has bled a lot, as they tend to do, but when I feel around the wound, there's no evidence of skull fracture. He's managed to break two bones in his foot, and there's a horrible bruise on his back.

It's taken me two hours to sort him out, and I'm exhausted.

He gets to keep the oxygen as we wheel him to the zero room.

JACK

They're OK. I mean, they're not OK really, but they will be. They're alive, anyway. I should have spotted what was wrong with Martha, I was just too set on finding and then treating the Doctor that I barely looked at her. She could have been still dying.

She wants to go to her own room and sleep, but I don't let her. I make her use one of the other examination beds in the medbay, and she's too tired to argue.

They're both sleeping, both healing.

I don't know what to do.

I head to my own room, strip, and step into the shower, but I can't seem to rid myself of the stench. It's not the rotting smell of the compost, nor even the smell of death that clings to me even after resurrection. It's the stench of guilt. I dress in a fresh shirt and trousers, and leave Martha and the Doctor sleeping.

Outside the TARDIS I try to atone for my mistakes. The bodies are not all dead, and I manage to save quite a few. They're no longer tough security personnel wielding lethal laser disruptors; they are lost and frightened, in pain and confusion. I think of their sterile forcefield world, and I wonder how long it's been since their lives were last out of control, how long it's been since they were last in a situation that's not completely regulated.

I almost wonder how long it was before we arrived that they'd ever had cause to fire one of their weapons.

I think about the way they put my body in the neatly categorised trash, as if they didn't know what to do with it; about the way they'd obviously tried to drug Martha into compliance and then panicked when her body had reacted unexpectedly; I try not to think about the way we arrived in their ordered world and tore it apart.

I don't know what else to do. I go back into the TARDIS and close the doors, leaning against them and sliding down so that I'm sitting with my hands draped over my knees. I wait.

THE DOCTOR

That's better. It still hurts to move, but it doesn't hurt to think any more. Jack must have put me in the zero room. There's a timeless calm here that doesn't exist anywhere else. The whole universe could be spiralling into chaos but in here it would be a single still point of serenity.

Which is why I don't deserve to be here, now I've remembered what's happened, and what's we've done.

Sitting up hurts, but when I test my feet on the floor, they seem to be able to support my weight. I leave the gurney from the medbay behind, and make my way out of the zero room to seek out my companions.

Martha is asleep in the medbay. She has her own oxygen, but when I check her condition, she's OK. I close my eyes in relief. They could so easily have killed her. Even if they didn't mean to. It doesn't take me long to confirm what I feared. The drug they had given her wasn't a poison, it wasn't even a drug that's useful for interrogation; it was just a mild sedative – something they would have on hand to help calm someone down. They would have no idea that it could cause an allergic reaction, and it's only luck that they had the powerful antihistamine on hand.

I leave Martha to sleep it off.

Jack is in the console room, sitting with his eyes shut and his head leaning back against the doors. He doesn't see me.

I want to tell him it's not his fault. But that would mean that it's my fault. So I make myself do what I should have done when we first picked up the energy readings and decided to investigate. I sit down in the jump seat and ask the TARDIS to hack into the base's historical records.

I read about a crashed colony ship on a deserted moon, retaining enough of their technology to start again.

I read about how they formed a closed community, which for 25 generations had fed off the life-giving geothermal radiation that gave them what they needed - a constant and reliable supply of unbelievable amounts of energy.

I read how they had had so few material resources that they had instead replicated the crashed ship's own forcefields to build something solid out of energy.

I read about how the laser disruptors were something salvaged from the crashed ship, and how they'd never had to use one in 10 generations. Until we arrived.

At some point Jack and Martha have come to stand behind me, and I leave the article on the screen so that they can read what I have just read. I know when Jack's finished because he puts his head in his hands. Martha doesn't move, but there's just the tiniest hitch in her breathing, and I don't have to look behind me to know that there are tears on her face.

These people - on the base below us - are brilliant. They've made something out of nothing. They brought order out of chaos. They crashed on a barren moon, and allowed life to flourish.

And our casual, self-righteous curiosity has just plunged them into chaos again.

Suddenly I'm grateful for the agony in my shoulder. It is a reminder that there are consequences.

...

MARTHA

'No, not that one, this one, the paler one,' the Doctor hisses. His right arm is still useless – he's hating that - and this is a job for four hands. Jack is holding the two ends of the main power node together, while I try and follow the Doctor's impatient instructions for reconnecting the frayed ends. We've been trying for the last hour to restore power to the artificial gravity and internal forcefields – and the lights, for that matter. Everything that Jack blew up.

It's not his fault. Not really. But I can see he thinks it is – it's cold in here, but the sweat's standing out on his face as he puts everything he's got into holding those cables steady.

The Doctor is blaming himself. That's why he's so short-fused – that and the fact that his shoulder must be absolute agony, and he knows that this whole process is taking ten times longer than it should because he's having to tell me how to do it rather than just fix it himself.

But we are getting there. Each of the damaged power nodes must have hundreds of separate broken connections, and I'm well over half way through.

We don't have a lot of time. As far as we know, the locals have no idea we're still here, and I think that's the way the Doctor wants it to stay. He doesn't tend to stick around for the clearing up, so I'm sure once the power's back on we'll be on our way – on to the next crisis.

Or maybe it's different when we've caused the crisis?

I have to pause for a moment to stretch my fingers – after an hour of this, my hands are starting to shake. I close my eyes for a moment – they're stinging and aching - and rotate my head left and right to get rid of some of the tension in my neck, then re-focus on the task in hand. I try not to think too hard about the fact that the TARDIS is having to hover in what is currently mid-air, and that the only thing holding her steady is a piece of taut string. Especially as the Doctor's the one holding the string, and last time I glanced round he looked like he might be about to pass out.

THE DOCTOR

I really hope the TARDIS can maintain this position. I'm sure the old girl will try her best, anyway, as I don't think any of us fancy another fall. Martha is doing well. She doesn't complain. Jack's doing what Jack does. And I can't do what I normally do, so I'm stuck holding a piece of string in my one working hand so that I can keep the TARDIS in position at the same time as I lean out of the door and tell Martha what to do next.

I've hinted to them that we just need to reconnect the power and then we'll go. I think Martha would want to stay and help tend the wounded, even apologise perhaps. Jack would happily fill their water replicator with Retcon.

These people will never be the same, though, whatever we do. Three dead in a small population could be devastating from a genetic point of view, never mind psychologically.

I genuinely don't know what we should do. When did I get indecisive? Mind you, when did I get clumsy and careless with people's lives?

Is it better that we just disappear once we've restored the power, or do we stay and try to make sure that this the moment when this isolated accidental colony rejoins the rest of the galaxy? Either way, we've changed things.

I close my eyes for a moment, and feel my way along the infinitely complex network of timelines, trying to sense points of divergence, points of weakness, points of danger. It's all in flux. I'm beyond exhausted, and in pain, but I force myself to go deeper still, seeking out the solid strands of 'what must be' and 'what cannot be', but there's nothing to catch hold of, it's all constantly shifting.

A stifled scream brings me back to the surface again with a jolt. It's Martha: her knuckles are almost white against the doorframe and we're hanging a foot lower than we were. I silently curse myself for not being able to complete the simple task of holding a piece of string in position, while outwardly I mutter an apology.

JACK

I'm not sure how much longer I can do this, but we're close now, really close to having everything reconnected, and if I didn't already have both hands occupied I'd have reached the stage of crossing my fingers that this is going to work.

'Last one,' the Doctor says, softly, and I expect it's for my benefit. He's been craning his neck to be able to see the final few connections being made. I don't know what happened when we dropped a foot a while ago; maybe he lost his concentration for a moment – not surprising, really, he must still be in absolute agony, and his skin still looks grey and almost translucent from the blood loss. He ought not to be up and about at all, and nor should Martha, for that matter. But I think they both want to do whatever they can to fix some of the mess we've made, and the quicker we fix what's fixable, the better for everyone.

The Doctor seems to think we just need to get the power back online and then we can go. But I'm not so sure. If this was earth, and if this was Torchwood, I'd not hesitate – chuck Retcon in the water replicator and plant a cover story to explain away the deaths.

But this isn't Torchwood, and these people aren't even human – there's no guarantee that a memory repressor would even work, and the Doctor would never let me use it anyway. And how do you explain away three deaths in a way that even begins to make this alright?

I wonder what he's really thinking. He's barely said a word, and there's been a cold distance in his eyes every time his focus shifts from keeping an eye on Martha's handiwork.

Forget whether I can keep doing this, I'm not sure he can. The muscles in my arms are counting the minutes and seconds until we can all breathe easily again.

MARTHA

My fingers are aching fiercely now, and stiff with the effort, but it's so nearly done. The last of the connections has been fixed, and the Doctor resets the sonic and hands it back to me. We've scraped together enough of the insulating casing to seal up the newly-fused connections, and the sonic makes short work of softening it enough for me to mould it into shape. Only when it's all covered and set hard do I look back over my shoulder for the Doctor's approval.

He nods. That's all. He's paler than ever, and I don't know where he's gone inside that head of his. I'll be worrying more about that later. But a nod for now means I know I've done OK. I've done in just over an hour what he could probably have completed in a matter of minutes, but it's done. I silently let out a breath.

THE DOCTOR

I hold the string steady while Martha and Jack climb back in, then very carefully wind it in as I approach the central console, all the time sending telepathic gratitude and calm towards the TARDIS, and enjoying the warmth of her response in my mind. There's only a slight bump as I unhook the string and allow us to land again.

I can see the relief on my companions' faces, and I'm slightly surprised that Jack, at least, still hasn't thought through the implications of the base having artificial gravity. Because we're so not finished yet, and the really tricky bit is still to come – switching everything back on.

And I'm still not quite sure how to do it without causing chaos all over again. I don't think we can, and still make a clean getaway.

It's actually Martha who works it out, though her first thought is about the forcefields.

MARTHA

'Doctor,' I begin, assuming that there's a simple solution to the great big

glaring problem we're facing, and that he just hasn't explained it yet. 'How can we reactivate the power when we don't know where everyone is? I mean, what if there are people standing or lying right across places where there'll be forcefield walls once we switch it all back on again? Would that be dangerous? Or are there – I don't know - safety cutouts or something?'

'There might well be safeties,' he concedes. 'But whether they're working at the moment? It's not worth the risk.' He takes a long breath in through his nose. 'And we need to work out what to do about the gravity, too. We can't just switch it back on again, even if it's not as long a fall this way.'

A combination of memory and imagination instantly show me a vivid picture of what it might be like if we did just switch the power back on. I suppress a shudder. We can't do that.

It's Jack who suggests a solution. It's very Jack, and I don't really it, but at least it will work, and it's better than the alternatives.

JACK

We don't use compost this time round. There are more refined ways of gassing the population of a moon base than igniting rotting waste. I can tell the Doctor still doesn't like it, but no-one else has come up with a better plan.

And this way I'm the only one who has to cope with the sudden, lurching, nausea-inducing return of the artificial gravity, because the local population are all safely unconscious in the TARDIS, with Martha and the Doctor ensuring that they stay that way until normality is restored (as far as it can be). It also means that I'm the only one who has to cling onto a power node with one hand, hoping that my legs aren't going to swing into the path of a forcefield once I switch the power on.

Everything comes back on at once: bright, white lights, gravity shifting by ninety degrees, and all the walls are back. The power surge that rips through me doesn't quite kill me outright. I think it's the force with which I hit the wall, and the sickening snapping crunch in my neck that will do that. I prefer it when it's quick.

MARTHA

This is better. This has to be better. We're not going to try and tamper with their memories, but at least we can tend to the wounded in the TARDIS' own stable gravity field, while Jack sorts out the power, then put them back in their base with everything the right way up.

I hope Jack's alright. I try not to think too much about the detail of what he's doing. Mostly I'm glad it's not me swinging from the power cables while the world tilts around me. And it can't be the Doctor. He only has one working arm, and he still looks like he's going to keel over any minute. But is Jack's like worth less for the fact he can't stay dead?

I focus on doing what I do best: taking instructions from the Doctor again, I draw on the full range of the TARDIS' formidable medical equipment to try and make sure that when we do leave here, we leave everyone in as good shape as we possibly can. We owe them that, at least. And as the Doctor pointed out, there's no point withholding advanced treatments from their future when the timelines are all in pieces anyway. Maybe that's why he's looking so distant – he's trying to work out if we've torn a hole in the universe as well as wrecked a moon base. Talk about seeing the bigger picture. I almost laugh, but I think it's the nervous energy and exhaustion kicking in, because none of this is funny.

THE DOCTOR

Martha is brilliant, she really is. She just takes everything in her stride. And she knows when to just get on with it and swallow her questions. I'm sure I'll get an earful later, and I'll deserve it.

I've half an eye on what Martha is doing, but most of my concentration is focused on the timelines. There's still so much in flux, but it is looking better. We're doing the right thing so far – or quite possibly, one among many potential right things. No parallel universes yet, and no significant changes to the future. I breathe a sigh of relief as it starts to look as if this is one of those situations where the universe simply compensates, and heals itself.

A shudder passes through the TARDIS, and the lights flicker for a moment. Martha looks up, alarmed, and I reassure her that it's just the TARDIS compensating as the power coming on again outside. Jack must have made it all the way up to what used to be the power distribution room. Now I've thought of him, I can't help but sense his death, followed a few minutes later by the nauseating jerk that signifies his return to life. It's at times like these that I ought to be glad he is what he is. But that doesn't stop me being constantly aware that he's an endlessly living and breathing temporal anomaly worse than anything we could ever have caused here. I almost laugh, but none of this is funny.

MARTHA

We need Jack back before we can start moving my still-unconscious patients back out into the base. The Doctor can't lift anything, and they're all much bigger than me. When I open the TARDIS doors to see if he's made it down again yet, the brightness is almost blinding after so long in the TARDIS' more subtle lighting and the stifling darkness and chaos of the power failure.

It's remarkable how little mess there is; by the time we've piled it against the nearest wall and sorted through it to salvage what's intact and what can be mended, it's clear that the whole lot would fit into my old flat back home, and this is supposed to be for a colony of people. We already knew that the base was constructed using forcefields, but I still can't get over how little actual stuff these people have.

'No minerals worth mining on this rock,' the Doctor comments, when I ask him about it. 'All they have is energy, and there's more than enough of that. So they replicate their food, and use the same few scraps of raw metal salvaged from their own ship for the things they need that can't be created from raw power alone, recycling everything again and again, for generations.'

He's still very distant, but I can hear the admiration in his voice.

He crouches down next to what must be one of the replicators, and fiddles with the connections one handed, the sonic clamped between his teeth. We have to make sure everything's working properly before we bring our unconscious patients out of the TARDIS and put them back in the base ready to wake them up.

I wrap my arms around myself and shiver. The environmental controls were compromised during the power cut, and it's freezing, but now everything's back online, it should warm up again. When Jack gets back we'll be able to start moving people out.

JACK

The difficult bit is finding my way back to the TARDIS now that the walls have been switched on again. Every corridor looks the same, and there's not even any debris here, since the forcefields came online instantly, and the gravity had a split-second delay. Everything back to the sterile uniformity that we found when we first arrived.

Except that three of them are dead.

Running along the corridor's doesn't help – the silence of my footfalls on the energy-constructed floor just makes the whole place even creepier, and a big part of me will be glad when we can leave here and never come back.

The Doctor has his good hand stuffed into the depths of some machine or other, but he's already looking up when I come round the last corner. There's an apology in his eyes, and I nod in acknowledgement before turning to Martha and wrapping her in a hug that we both need.

Between the three of us we mend everything that can be mended, and I take the unsalvageable scrap to the waste disposal room. It's only as a press the nice red button to open the door that my stomach lurches at what might have happened in here when the forcefields went down.

I almost laugh out loud when I go in and find it as ordered as ever. This must be one of the few areas on the whole base that used real solid construction, and it's all still tethered to the external wall. I've not seen anything else that's not energy-constructed – as I run a hand over the hard edge of the nearest container, I think I know how the Doctor must have broken his foot and bruised his back as he fell.

I can't help thinking that, in retrospect, a few bruises and a couple of broken bones are a small sacrifice to make in return for not being covered in compost and raw sewage. Things could have been worse during the power cut after all.

I dump the scrap, and head back to the TARDIS to help Martha evacuate the sleeping base-dwellers. We don't know their names – or even their species, for that matter. But they're in better shape now than they were, and I start to wonder whether the Doctor will decide that it's time to go – time to leave them to work their patchy memories of the day's events into their history and get on with their lives.

THE DOCTOR

The timelines are drawing together. The tension in my mind finally begins to ease as gradually the stray strands coalesce into fewer and fewer distinct possibilities and the rawness of the moment heals. Nothing is completely fixed, but it seems more and more likely that whatever we do here, the universe will remain unchanged. The instability was our mistake, like dropping a stone into water, but the ripples are fading.

Even amid the relief, I grieve. It seems a terrible injustice, that these people who have worked so very hard to create a life for themselves, and who made this barren rock a place that could support them and their families for generations, don't even create the tiniest hitch in the warp and weft of infinite possibility. These people should matter. They're brilliant. But it is as if the universe doesn't even care that they exist. They die, the live, and nothing changes.

But I bet I can change that. There's a time when I wouldn't have even considered it. When we watched, but never interfered, lording it over the universe but never getting our hands dirty.

But there's no-one else left now. No-one to tell me I'm wrong (well, nobody that I can't ignore) and, well, the universe might just have to compensate again, and make room for these brilliant people to rejoin the story. They deserve better than this rock, and I can give it to them. I can, and I will.

MARTHA

It's as if there's some kind of battle going on in his head. I wish I knew what he was thinking.

But when he does explain what he's planning, it's like I'm looking at a stranger. He waves off Jack's objections with talk of the universe compensating as if the universe belongs to him. But it doesn't, does it? I mean, he's a Time Lord, but nobody should have that kind of power. We screwed things up today, but how far can we really go to put things right?

He's pacing up and down, but he's as pale as ever, and there's a sort of manic energy about him that scares me. I feel small and fragile as I approach him and look up into his face. There's a sickening moment when he looks down and through me like I'm nothing – really nothing, not just like usual – and I don't know how I find the courage to speak.

'Doctor, listen, please. Can't we just give them the choice?'

He deflates, and blinks, as if seeing me for the first time.

'Yeah,' he breathes, finally. 'Yeah. Their choice.'

I let my head fall onto his chest, and his one good arm feels heavy and solid as it wraps around me.

It's been a long day, but it's so nearly over.

...

THE DOCTOR

I think back to that day once in a while.

One day, I think, they'll call. They'll transmit the signal I left them, and I'll come, and I'll take them wherever they want to go, let them have the whole universe as their playground.

How many times have I stopped myself from going back to check?

Their choice. Always their choice. I owe them that.