11: Eurydice's Footprints

It's a soft little knock, knuckles on glass, but when it hits his ear it's a gunshot. A ten gun salute; cannon fire. The eruption of fireworks, of war. This cacophony, this head-ringing explosion that's got his blood pressure soaring, lungs squeezed tight, heart galloping out an adrenaline overdrive: it's imaginary. Nothing's happened, not yet.

It could, he supposes, have been anything. A delayed reaction to painkillers. Exhaustion. The discovery of a semi-sentient quantum mnemonic engine called Bad Wolf that has shaped the edges of his life for years like wind erosion.

But there's something he recalls so vaguely: some dream, some half-remembered thing that stalked the jungle of his restless sleep.

No. Not dream. Not sleep. A hallucination. A picture in his head.

A double-decker bus. The smell of hot vinyl and the powdery grit of sand. An increasing feeling of unease. And something about knocking. A warning.

What he'd only thought was a hallucination, a glimpse through a telepathic window between his current and original selves. But none of it explains the surge of absolute primal fear where he feels like he's suffocating inside his own skull.

When he looks up, at Rose, she's smiling down at the binder still open to the program credits page, oblivious to what he supposes is just some kind of panic attack. She reaches, touches the printed cyrillic letters with the tip of her index finger. On her face, it's the kind of smile that doesn't go all the way to pinch up the edges of her eyes.

"The program," she says, inclining her head. "I named it. You can read it, right? Even without the translation circuits?"

Of course he can. And of course she did. The Bad Wolf creates itself. Here's just the far end of one of those colored loops, the swinging pendulum connecting its own loose ends to make a circle. The ultimate ontological paradox, the only possible exception to the second rule of thermodynamics. An idea cannot age; words are unaffected by entropy.

It's made his hands go cold, these things in time and space he can't fit inside his head. Loop anomalies, entities of energy. The realization comes with a sinking feeling, a kind of nebulous haunting dread that crawls hand over hand up his spine. With his throat dry, he nods, avoids her eyes to hide the burn of tears he's blinking away.

There's a loose leaf notebook paper, folded and pressed under the title page like a bookmark. It's handwritten in different pens, some blue, some black, some felt tip, one pencil. The sentences bend like they were written without a solid surface.

25 Sept 06: v2-Junction of Little Sutton/Ealing Road, right toward Griffin's Parade

24 Dec 06 v1-Thames flood barrier/v2 Public House Pub

4 Jun 07 v2-Chiswick, Chowdry Raffle Ticket

25 Dec 07 v2-Firborne House Hotel

14 Aug 08 v1-Adipose Industries/v2-Number 29 Runswick Place, Leeds, West Yorkshire

19 Sept 08 v1-UNIT/v2-Torchwood, Sontar (*Telescope)

10 Oct 08 v2-(Betelgeuse, Bellatrix, Rigel, Salph) Hilltop, Leeds

25 Sept 06, 10:01 AM: v1-Little Sutton Street/Ealing Road-LEFT toward Chiswick Highroad.

"The machine leaves traces of itself?" Somehow, he barely recognizes his own voice.

"An energy signature: the encoded name of the program. It's so the machine can track where it's been, events it's accessed. And operators can recognize the hallmark in-universe, like an editor's mark."

"So it's been you all along." It feels ominous when he says it, although the sentence rides out on what's almost a laugh. It's like he's accusing her of something. "You were always this..."

Waiting for me. All this time.

For whatever reason, he feels raw and heavy, made of stone and hot coals, gravity pulling everything inward, compressing like the remains of a dead star.

Rose, she's pretending now, pretending not to know this is the end of the line, that this is the bottom of the well with nowhere to go but back up. And not together. She smiles, but not really.

He's already been cycling coordinate sets, familiar with the control after a few minutes of studying the interface, number pairs specific to spacetime variables. Digits that represent a given planet in a given orbit length around a specific star out of a septillion at a certain point in its orbit around its galactic center all at the rate of a few hundred-thousand miles per hour. Everything is moving, hurtling through space, every moment a slingshot toward their final inevitable destination and this is what they've come for. This is why they nearly drowned. And they cannot stay in this bubble universe, this unstable temporal pocket, no matter how much now he would want to try.

Because this is what he gets.

"Rose," he begins, still jittery. There's something in his head that's clamoring, the peal of warning bells too loud to hear even the warrior's march of his own heartbeat. "You remember what I said, earlier...how...this is a state where collapsed mass shouldn't exist? And interaction with surrounding matter is critical because it limits the amount of simultaneous superpositions with which you can interact? The observer effect?"

"That attack we both had. Like vertigo, I remember."

"Did you see anything? During that time? Any kind of, I don't know. Dream isn't the right word."

"Like did I hallucinate?"

"Maybe? Yes."

"I don't...think so. Not sure I remember properly. I felt more like I was getting off a ride at a funfair, just...you know. Worse," she drawls, pulling half her bottom lip into her mouth and worrying at it a moment. "It'll be a problem, won't it, after you go through?"

His head jerks toward her so fast, just for a moment it feels like it will disconnect and launch off his neck and go tumbling end over end across the floor. "After I go through?"

"Doctor," she says, and drops into a crouch, her hands clutched on the doorframe and then on him, crawling closer to look up into his face with her eyebrows pinching together on her forehead. "You said, from the other side, you could find Mum. Why couldn't you find me the same way?"

His mouth works, but nothing comes out. On all accounts, she's right, and he could, but he won't. He can't. His stomach knots around itself at the suggestion.

"I just need some time. Just a little, to find another way. If I dismantled-"

"And what if it never works again?" she spits. "What if you need parts, tools, something we can't get here? You said it was unstable, that this whole reality will collapse. You didn't even want to wait for stitches, now you want to wait to rebuild the machine?"

It's true. All of it, and he flushes at what's implicit in her words, the questionable nature of his caution when contrasted against what he had been willing to wait for. He can't argue, and he can't explain it, but he's not going through and leaving her. What he is going to do...the only thing his conscience will allow, every instinct tells him not to discuss it. To just make it happen. It's easier to apologize than ask permission. Someone had told him that once, and it seemed like it was true.

And it goes against everything he's promised himself about Rose. About this last chance he's been given, about not deciding things for her. About saying goodbye.

He drops his hands. For slow-motion minute, he does nothing at all. Doesn't speak. Just stares, head down, shoulders forward.

"Rose...what if..." he clears his throat, tries again with his eyes on the plotter screen, the multi-layered rat's nest of interconnecting arcs that are easier to look at than the expression she's about to make. "What if we sent you through first?"

"Not gonna happen."

"I have a better chance of dealing with the disorientation... I can't be sure what will happen, what that does to a body. What it will feel like, Rose. I can't let you test it."

"Oh, so then it should be you? You're human now, you may fare just the same as me. "

"Just a bit human, thanks. I still have adapted biological equilibriums to disagreeable climates, partial vacuums, extreme temperatures, brain chemistry evolved to acclimate to temporal flux. The Time Lord genome evolved to withstand temporal anomalies, Rose. And we have to choose one of us, don't we? Either I go through and try to fish you out or I send you through and follow. Though you'll have immediate recognition with Torchwood operatives and I'd likely be isolated until Pete could vouch for me...if Pete would vouch for me. You said it yourself: we can't stay. We came here for this. We risked our lives. So let me send you through. That way, you'll be safe-"

"Oh no. No, Doctor, you aren't doing this to me-not again. Not again! How many times are you going to send me away for my own good against my will?"

He heaves out a breath. No matter who leaves, it's gone both ways, and he's just falling into another old habit. There's no denying, he's both sent her away and left her behind, and never even turned to look back. Never said goodbye.

He reaches, both hands circling her wrists to tow her back into the tiny glass control booth. "This is different."

"No, it's not."

"I'm asking you, Rose."

"And I'm saying no. I don't want..." She doesn't finish, only collapses forward like a falling tree, hands over her face before making fists around handfuls of her hair. "I can't. Not after all this. You go through and find me. I know you can, Doctor, I trust you to find me."

He closes his arms around her, the open binder trapped between them, D-rings pressing uncomfortably into his abdomen while semi-resists, and he can't help himself.

"Do you, though?" he asks into the blonde cloud of her hair. "Trust me?"

With the apple of her cheek balanced on his collarbone, she nods before looking up. Desolate and wet-eyed; she intends to look angry at the question but can't quite manage it.

"What if you don't, though?"

"Don't...what?"

"What if you don't have those things? Your brain chemistry...biological...things...what if you don't have them, and you're just as vulnerable as I am? It happened to you, same as me. What if I go through and you're too incapacitated to work the controls? What then?"

"I'd know it, Rose. You're overestimating the quantity of human structures the metacrisis spliced into my genome. But. In that case...the...same way you imagined I'd be able to find you."

"That's not an answer. I imagined you'd have built some kind of gizmo out of copper wire and drinking straws that could track me down, translate Arabic to Portuguese and melt chocolate in one go."

He laughs teeth flashing in the half-dark, eyebrows springing toward his hairline.

"The cannon is all we need. We're in the right place, but in-between seconds. This machine peels all that apart, like stretching fabric to its limit, until you can see the warp and weft-every space between the threadwork. You said as much yourself. It can track anything given the right start point. The swinging pendulum, Rose! We pinpoint a theoretical continuum coordinate running one second ahead of us to properly calibrate with the boson decay of the surrounding matter, calculating for planetary trajectory, stellar drift, galactic torsion, time dilation..."

When Rose looks uncertain, he continues. "Remember what Byron said? They couldn't get a lock on on the event-time of our location. Their coordinates could only correspond to an event in Euclidean space, not the degree of temporal separation. But we have all this power here in front of us. We have Bad Wolf. We just need to move, one geodesic second forward at the same invariant spatial interval, and in doing so, our particle decay rate can synchronize with the proper relative frequency. That's all. C'est tout. Just twenty minutes without an observer, and I reset the navigation relative to my start position. At worst, I'll only be a second or-well, not far behind you."

"Sort of like 1879 instead of 1979, huh? Werewolves instead of Ian Dury?"

"We still saw Ian Dury, after. You liked the werewolf, Rose. And you won ten quid-"

"Cardiff instead of Naples? 1953 London instead of New York? Wrong year, wrong city-you can't blame me for doubting your maths."

"It's not my maths. Time cannot be traditionally separated from spatial coordinates," he scoffs. "All physical phenomena happen independently of the reference frame. Mathematically, spacetime is a single manifold consisting of events, occurring at a certain spatial location at a certain interval-these restrictions correspond to a particular mathematical model which differs widely from Euclidean space in its manifest symmetry."

"You're just trying to confuse me."

"No!" The Doctor steps back, inhaling slowly, passing his hands over his face, fingers pressing into the globes of his eyes before plowing back through his hair and hanging clutched like bony spiders on the back of his neck. "Rose, it's important you understand. Every event that exists is spatially linked to an immensely specific coordinate. Every where has its own when. Everything is barreling into oblivion at a thousand miles per second, wobbling through space in helixes and spirals, every coordinate in Minowski space changing by the microsecond with only the gravitational force to thank that they keep in any kind of constant pattern. If I'm a couple years or miles off, it's still an astonishing accomplishment of mathematics and ingenuity."

Rose resists a thin smile. "That doesn't make me feel better."

"What I mean is, your Torchwood scientists, they might tell you-you know, let's just pretend, just for a second, hypothetically, I don't come through after you. You'll need to explain to your cannon team they need to set the coordinates for something that doesn't exist. Rose, think about it. If there was a viable way to extract us from here from where they are now, they would have done by now."

Her encroaching smile fades. "Doctor. What are you saying?"

"I'm saying-timespace is a widely considered a single abstract. Time doesn't move independently from space. Their coordinates will account only for this, time and space as a single piece instead of..." He mimes a shape with his hands, like outlining the perimeter of an imaginary ball, but frowning and abandoning the developing analogy mid-gesture. "We have to set this machine to deploy at an event that doesn't exist in their concept of the science: a coordinate that's exactly the same spatially, but with a second forward only in the temporal separation. They'd tell you that you can't, that compensating for the time will automatically compensate spatially and send you two-hundred-thousand miles out into space where the Earth was one second before."

With increased agitation, he's biting down on the impulse to pace the room. "Trust me. They didn't build this machine on their own blueprints. They can't have. This proposed solution, Lorentzian coordinate transformations and geodesic vector tangents go against everything they know. I'm not saying it's not possible, it is, from the other end, it's just the same idea in reverse. I just...it would take some time to convince them to allow it, and for all that, you'd be here. Human biology in liminal space, setting aside the mental strain, everything points to pain on an exponential scale. And unlike your mother, Rose, you'd be awake for it. This is why I have to do this. This is why I can't go through and leave you behind- there are too many variables, too many scenarios where I'm not able to extract you without difficulties and red tape. Leaving you here-waiting, all that time."

"This is all because you don't trust Torchwood? And what about my mum?"

He deflates loudly, lets out a lungful of air. "Not all because, not even half-because, but I won't be entertaining a new opinion of Torchwood just now, if you don't mind. I said, it's possible and she's asleep-not even an observer to herself, in stasis. We can do a biologic signature sweep of the spatial coordinates of the hotel in Bergen for the zeroed out Euler characteristic."

"And if you're not right behind me? If I come through and you don't show up, I'm not waitin' five and a half hours-"

"Rose. Please. There are so many reasons-Torchwood protocol is only one. Got myself into a load of trouble in the past assuming agencies will just let me have free rein of their sensitive billion-pound equipment to execute maneuvers their understanding of science forbids. My biology is better equipped to handle liminal space. I'd feel...far more confident going about it from this end."

She closes her eyes and inhales slowly. She seems to count, to wait a long moment before reopening them, and when she does, they have changed. Her tears have blinked away; she's resolute. Wearing her soldier-mask, she gives an almost imperceptible nod. "Don't be a couple years off. Not even a day. Can you promise?"

"The solution proposed virtually prohibits error," he gestures to the screen, the Bad Wolf interface, and she doesn't reply. Instead, the air feels dense, cold, like clouds passing over the sun. A quiet, almost imperceptible change in the air like the first day of winter or a shift in barometric pressure.

Slow and mechanical, in the tense silence that's settled around them, he initiates a trajectory scan, then begins entering coordinates worldline-centric to the local galactic meridian.

Long: 179°, 56', 39.4''
Lat:0°, 2', 46.2''

Dist: 7,940±420 parsecs/25,900±1,400 light years
51.5036° N, 0.0183°W

With fingers made of lead, he runs a subtraction equation to strip out the time differential, and in the empty field, enters -0.01, bypassing the inevitable warnings. Emotion is catching up with him now, like air rushing back into a vacuum. It's tightening around his throat while the interface maps out a different imaginary noose: the predicted loop of the double pendulum that should sort everything. The trajectory of the future. Life as it can be remodelled.

With a few more one-handed maneuvers on the keyboard, the warm up sequence shifts to auxiliary, the mechanical beast lighting up with full power and without words, he holds open his hand for her to take. He wiggles his fingers at her, and quietly, she puffs out a sound that's almost but not quite a laugh.

Hands clasped, it's the slowest, quietest walk to the module base, a ten-foot by ten-foot black box with an open glass-inset door, the inside lined entirely with mirror and an almost palpable fluorescent glare.

Rose turns in the open doorway, silhouetted by gold light, and he's seen this before.

("I looked into the TARDIS, and the TARDIS looked into me.")

The traveller and her machine, the vessel and her namesake, inextricable from each other-the other side of his own coin. Somehow, it's only appropriate.

"I went back," she says. "Six different times, after Donna told me you were dead. I thought maybe, I'm just not getting there early enough. That Christmas Eve. I went back, a week, two weeks before. But no, it...it was so much further back than that. The point of intervention. That thing on her back. That one little change that goes through everything. It's like, the future you have today isn't the one you'll have tomorrow. Everything you do every day...

like dropping a stone in a puddle, yeah? All those ripples? That's how this machine works. It maps out all those little waves, and it finds where they originate, like you said. And then I go there..."

"I went back-" she repeats, shuffling her feet. "The basement at Henrik's, at closing time."

"Rose, your own-"

"It was an accident. When we started trials, the machine could only teleport. It could move us around in our own building, so we tried further each time. First in distance, then time. When they wanted to test a different year...they wanted something specific. A time and date and exact location. It's what came to mind, so...there I was. It should have been the alternate world. Where I wouldn't have been. Neither of us. But there I was, standing in the dark, watching myself meeting you. It's how we found out about the holes. How there were places we could get through. It's how we knew the walls were thinning out.

"From there, we did more test runs. I tried to think of random points we'd been, so I could verify, you know. Not interact, just... We tried the power station in Cardiff, the street in 1987 where my dad died. The day in 1945 where we met Jack. I knew I'd be able to tell exactly which world it was if I could recognize things I'd seen already. I didn't even realize at first...everywhere I went, I was leaving a path. A message, with the call signature. Without even knowing it at first, I was leaving a path for myself to follow. I went everywhere I could remember going, further and further. I went to the Gamestation."

"You could have paradoxed yourself right out of existence." He bites out that last word, drawing the syllables between his teeth in anger.

"I could've done. But didn't. Instead, without what I did, we wouldn't be here now. There's a timeline where you finished that Delta Wave. The temporal static made it inaccessible. There's a timeline where we never met at all. Where I made it out the door before being asked to take the lottery money. Another where Wilson was still alive when I did. A million different versions of the same fifteen seconds-"

"Oh! It parses timelines in fifteen second intervals?" he interrupts, jumping from severity to enthusiasm fast enough to give anyone whiplash. "Is the navigation based on the Gabor Patch tests?"

Rose gives into a tearful smile, a breath of laughter slipping through her teeth. She goes up on her toes, hands on his face, mouth against his. Somehow, it still surprises him every time. If he dared to hope past the next twenty minutes of his life, he'd hope that one day he'd be able to kiss her without being flooded with desperation. Without the knee-jerk certainty that it will be the last time he ever will.

But he can't lie to himself; it could very well be just that. So he kisses her like it's the end of the world, folding himself around her. She crawls her fingers into his hair, gripping, holding on.

And without saying it, this is what goodbye really feels like. Frantic embraces in a doorway, forgetting to breathe between the release and reconnect of mouths, white knuckles and swallowed tears: this is the kind of choking regret that words cannot transcribe. This is where spoken language breaks down, where it just becomes syllables and letters.

But goodbye is just a word. Like forever. Like love. And he's not saying goodbye, not today.

"Rose Tyler, I love you." It's an admission that feels surreal on his lips, words that taste like salt and beach sand, like the atomized carbon-ash of a dying sun. They're too small and not enough, and for whatever reason he can't discern, they sound so much like an apology. With his forehead against hers, he closes his eyes, but can't think of anything better to say.

Saying it aloud, not as some kind of trump card to win a competition with himself-well, he'd expected it to feel like something. A gust of relief or completion, a sort of epiphany, but instead he just feels empty and dark, like a sky without a star.

"Doctor," she whispers, and he's crushed under the weight of her voice. "You didn't promise."

"I know," he says, and kisses her a last time. "Better be quick."

In the bright glare from the open door of the mirrored chamber, her face is wet with tears. They grip each other another moment before releasing, and Rose walks inside the transmission module with a peculiar, stiff gate, the door sealing on a tripwire sensor behind her. From the control booth, he can see her while he calls up coordinates from memory, fingers moving, deft and efficient as if nothing is wrenching him in half.

Nine hundred years of time and space, awe and wonder but more often misery. A life lived running, seeking to participate with all the doom that's out of his control, a dance with the inevitable, a life lived for others and so rarely for himself. Luck has seldom given him even a noteable passing glance except in this glorious second chance, like being granted an afterlife. This magnificent gift, this reward in disguise as a punishment.

But no. Like everything has always been, he will sacrifice everything because he can't promise anything. Because the terror he'd felt before was real, and he's stretched the truth to convince her this is the safest option for them both.

Because this is who he is.

This is what he gets. Hisreward. And it's not fair.

When he initiates the activation sequence, he fights for breath. He will always lose; it was foolish to think this would be any different, that the universe wasn't out to punish him anew. It's possible he'll lose everything, even this wonderful pathetic body.

This body was born out of death. All it can do is die.

The Doctor bites hard against nothing, jaw clenched until it aches, and he presses deploy on the hadron-chronon generator. His shoulders jump only once with the effort it's taking to keep ostensibly calm and dutiful.

From inside the booth, far away through the heavy reflective walls, the sound of Rose's voice. Her hands are flat, spread against the glass inset in the module door. He can't make out the expression on her face while she calls out, but catches the words:

"Don't look back!"

There's light and a sound, a great roaring hum like something massive passing overhead. His equilibrium faults in the wake of the power surge, surrendering to a hot rush of dizzy nausea. Somewhere inside that eruption of light, Rose has vanished.

In the massive and deep silence that follows, there's the limping human heartbeat that's left behind, rushing in his ears, solitary and lonesome like a cry in the dark.

He only has to make it twenty minutes before the cooling sequence completes and the system will reactivate. He fights to look up, toward the empty module but the motion of head inspires a thunderclap of vertigo. His vision blurs, threads of uncertainty twitching between his fingers, a google of timelines wavering around him, his own wave functions unravelling and expanding, travelling in every direction at once, like something dissolving in water.

Without an observer, with the magnetic force haywire, mass capability fragmented, he spills to the floor. He feels, but cannot hear himself cry out.

With every muscle snapped tense, the agony wells up like liquid in his throat. He can taste blood. It's a feeling like his bones are heated like iron over a flame, glowing orange-red, his flesh melting off them like candle wax. He's being scattered, split molecule by molecule, taken apart.

"Carrot juice," a voice says, and he looks. Leaning over the console in a long ago TARDIS desktop theme is Melanie Bush. He hasn't seen her for hundreds of years. In her own timeline, she is long dead. She holds out a glass, almost shaking it at him. "I've told you before," she says. "Looking after your health is important even for a Time Lord. Vitamin A, Doctor."

He takes it, sneering at the bright liquid with an old familiar sort of disdain. Everything feels different. Everything. The pain, the wave functions trembling around him like a furious black blizzard, it's all still there, but also it's not.

"I tell you, it's making me go colorblind."

"Rubbish," Mel says, squinting around first and then straightening up and dissolving in front of him. Instead she's Tegan Jovanka, practically tearing out her hair. "Why do you always have some incomprehensible answer?"

His stomach twists inside him, and everything jumps ahead. In a field, staring into black space, Ace wipes her eyes with the back of her wrist. She places a hat-his hat-back on her head and stares into the field. He takes the hat back.

"Mine, I believe."

Tegan is gone. She was never there.

Jump back. A voice, yelling through a wall and the rumble of vibrating; the twist of the toxin crawling through him, the feeling of chasing death down before it reaches him. Or Peri. Because this is all his fault, and he will set it right even if it means crashing this thing. "Doctor! Unlock this door! What are you doing in there?"

"No, no he's a good man!" Jo Grant wails a hundred years earlier. She throws herself in front of him like she's protecting him from an explosion. "Kill me, not him!"

The timelines lurch again, jump far forward. There's a Dalek chained in the dark. The last thing he'd ever expected to find at the end of this quiet search, the last kind of dissonant, mechanical protest he'd ever expected to hear again. The anger is poisonous, rolling off him, a foreign and alarming desire to hurt-to inflict pain-to bring the same misery he's been left carrying around the deep empty halls of space and time on his own, wearing guilt as a slipcover to hide under.

It screams-and there is a swell of perverse joy. Because he wants it to scream.

("What the hell are you changing into?")

"We have accepted your plea," someone else says, in a dark room in a white robe. The Dalek is gone-was never there-replaced with a familiar Time Lord long before their demise at his hand. He can't remember his name. "That there is evil in the universe that must be fought, and that you still have a part to play in that battle."

"You mean-that you're going to let me go free?" The words barely want to make it out of his old throat.

The lord in the white robe seems to fight sounding amused. "Not entirely."

It's only a minute later he's stammering out a plea-then shouting. "But you...you can't condemn me to exile...on...on one primitive planet in...in one century in time...!"

And while he says it, he is all-knowing. He'd laugh if he had any control at all. If only he'd known then how much it only sounds like a punishment. How much it would hurt when it's taken away.

They make him change, and he cries out the whole time. No. No, no, no. Nononononononono. His most pitiful set of last words.

("I'm really glad that worked. Those would've been terrible last words.")

But it's a cold night in San Francisco. The sky is clear, there's a light humid wind, his shoes are a phenomenal fit and finally, he can remember...

"Only a killer would know that," Margaret says by candlelight, an entire lifetime and tragedy later. "Is that right? From what I've seen, your funny little happy-go-lucky little life leaves devastation in its wake. Always moving on because you dare not look back. Playing with so many peoples lives, you might as well be a god. And you're right, Doctor. You're absolutely right. Sometimes you let one go. Let me go..."

"We've landed, Sarah." But far be it from him for these stretching out timelines to have any kind of order. Maybe they do at that.

"Where?" she demands, sounding angry, even though she'd explained her packing was only a joke. She'd never intended to leave, but he can't take her to Gallifrey. He can't.

"South Croydon. Hillview Road, to be exact."

Or, he supposes now, not so exact.

Jump forward and it's the floor of the console room hard and familiar under his back, years and years after asking Sarah Jane Smith not to forget him. Sarah Jane with her sad eyes and fluffy white jacket, orchid pot under one arm. It's started already, the itch and throb of it, the regeneration he'd only hoped would come. "Oh, it feels different this time."

"How can she do that?" Val Cane cries hysterically, only a week before but centuries after. "She's got my voice! She's got my words!"

"But they won't say anything!" Susan insists, six hundred years earlier.

"My dear child, of course they will," he admonishes. "Put yourself in their place! They're bound to make some sort of a complaint to the authorities." He gestures to Ian and Barbara, half-blockading the doorway. "Or at the very least, talk to their friends...If I do let them go, Susan, you do realize that we must go too..."

"No...Grandfather..."

"There's no alternative, child."

"I want to stay!" And so she did, so she did. And how he should have listened, but he was so young and obstinate, forcing his will on others because of what he deemed best. It's been a long, difficult lesson-but he may have finally learned it.

("Goodbye, Susan. Goodbye, my dear.")

"Butwould you do it?" He feels the words come off his lips-a set of lips long remolded into others several times over. There's a scarf tight around his throat.

"Yes...yes..." Davros replies. "To hold in my hand, a capsule that contains such power...to know that life and death on such a scale was my choice!"

"A hand!" Martha Jones says long afterward and a trillion years in the future, eyes gone round and focused tight on Jack Harkness, who gives one of his megawatt poster-boy smiles. One day that pretty face will be all that's left of him. "A hand. In a jar. In your bag!"

I don't hear anyone knocking, do you? This one, just a voice in his head. His own voice, but also not.

And then another voice, beloved and unmistakable but faceless, called out only moments before the webwork of his life had undone around him, the words ricocheting back in the cavern of his skull: Don't look back!

He's never been any good at doing what he's asked. Or told. Not that this was always intentional.

Don't look back? There was nowhere else to look, and there was no control. He can barely feel his body, his fingers gripping at handfuls of his hair. He'd heard before, how your life flashes before your eyes when it's all over. He breathes deep, timelines tugging on his eyelids, spindling out on every vector imaginable. Chess with Leela. The sensory whiteout of the fog in the Gallifreyan Death Zone. Equation games with Adric. The airless scream of the Nightmare Child. A cargo ship drifting into a living sun. The voice of the White Guardian.

Christmas snow in 1895 Cardiff.

A grinning blonde in period dress, and the Doctor's favorite feeling: falling in love. Laying his eyes on something wondrous and previously unseen, like seeing the burning wheel of a newborn sun in variable star v838 Monocerotis, the toxic downpour of mercury rain, brilliant emerald pillars of luminous dust and gas four light years tall, flash-frozen ocean waves twelve stories high, the cinematic slow-motion cataclysm of colliding galaxies. Something magnificent, discovered.

He'd just never felt it for a person before.

In a fetal position in the collapsing liminal state, the Doctor shakes, his entire body reduced to raw nerve endings, a boil of cold bile burning in his throat. Pain lances from his stitched arm, up through his shoulder blades before plunging down his spine. It's the feeling of slow suffocation, the pressure increasing, everything pushing and compressing from all sides like it's alive and breathing, his skin prickling and crawling with the feeling of phantom insects.

Don't look back, she'd said. Don't look back.

("If you're paying attention, Rose Tyler, it means we're both a pillar of salt.")

She's not wrong. This will be the end of him, and here he is: Orpheus following Eurydice's footprints back into the fire-though instead it's a cross-section of the width and breadth of the entire miserable burning wreckage of his life so far. There are better ways to spend his last breath than choking on regret.

But there is no forward. Not anymore.

"Doctor," Rose says from somewhere, and his vision clears vaguely. He's at a kitchen table, sitting with tea in the TARDIS galley, and Rose gives him a thin, almost apologetic smile. She's asked him a question he can't remember-can't ever remember sitting here this way at all. He palms the teacup and leans back, exhaling a lungful of air and feeling the compression in his chest. It only takes a moment to notice he's only got one heart, and there's a feeling like a needle pushing into it, like a butterfly being pinned to an insect board. There's an unpleasant sentiment simmering in his gut. Jealousy. His palms itch with it.

Rose casts a gaze over her shoulder. All this showboating and lip-biting and looking at the table top, and she still hasn't quite come out with it. "I don't want him to overhear, obviously. I just...maybe you'd know what I should do."

"Ab...about what...exactly?" It barely sounds like a voice; it's soundless like a thought. He's not even certain it's in English.

"About that I've been back six weeks and he still won't even touch me. What am I doing wrong?"

She means the other Doctor. And he's only opened his mouth to shakily reply before everything lurches, shifts and remakes itself like a bubble of mercury. Now Rose is in the doorway to a different kitchen, and instead of a teacup she's hefting a tiny white-blond girl in a black and green jumper, shifting her onto one hip and looking delightfully irritated, talking out of the side of her mouth in an almost conspiratorial way.

"If we don't leave for the airport now, Gemma and I have decided we're getting on that zeppelin without you, Daddy." She jostles the girl a bit, leaning in to speak close to a small ear buried in a towheaded fluff. "Aren't we?"

The tiny girl squirms and throws her arms out, little hands balled into fists with the intense enthusiasm only achieved by the very young. She exclaims a wordless agreement with a four-toothed grin.

"And as a result, with your absence at another summit, you can kiss that CERN funding goodbye. Or auf wiedersehen, I s'pose."

"Well. French is predominant in Geneva," is what he says, nonsensically-it doesn't reflect the volcanic storm boiling up inside him. He sounds so calm when inside he's heaving, frothing, twisting, wanting to jump forward to embrace them both furiously just for the fact that they exist anywhere at all. "But I can think of other things I'd rather kiss-"

He stands from his chair and moves toward them, too slowly, what he says next utterly drowned by a sound, first like wind, then the scream of feedback. It's the sound of his heart spilling open. Soundlessly, Rose is laughing to the soundtrack of a blaring alarm, Gemma squealing with absolute silent glee while he kisses the bottoms of her tiny bare feet.

The cooldown sequence is complete.

But he doesn't want to go.

Not from here-not from this. He can't hold onto it. Like river water through a broken flood barrier, the timelines twist in shape after shape.

We will sing to you, Doctor.

Quick as a scream, everything else tumbles afterward, the potentials: his possible life in superposition. Donna and Rose in swimsuits, running down a beach with fine green, copper-based sand. His mouth tastes like coconut, and he's happy.

Martha Jones invents the first quantum transmat system, he's there at the presentation for her first Nobel Prize. Jack and Ianto's wedding: spectacular cake, even better music, dancing until sunrise. He takes Wilf to a planet covered in dry hydrogen ice, a hundred-million years before its first civilization, and watches the old man make snow angels like a giggling child.

Then he saves Luke from a speeding car. Mickey and Martha run from a Sontaran onslaught. Jack sits inexplicably in a dive bar on Deneb-19 with Midshipman Frame. Donna's third wedding-the only one she'll remember-and a lottery ticket. The kind of gift only the hidden silent Donna would properly appreciate.

And Rose: young and grinning, doe-eyed in the falling snow. He's in pain just watching her walk away. She doesn't know him yet. In some realities, she never will.

He wants to open his mouth, to call out to her with the intensity of a holy confession through the cold air, a plume of hot breath containing everything he'd never said. It's New Year's but he'd wanted Christmas-just in remembrance of one evening already long past. Paper crowns and new teeth: the first instance in lifetimes that he'd felt at home.

But he still doesn't say goodbye. He knows now, his fear of endings is nothing pitiable. Nothing noble. It's just...

Human.

Ironically it's a frailty he'd developed long before he'd actually become one.

It's taken the rushing liquid pain in his chest to bring him back to himself, and it takes a moment of reorientation to locate the sound, and sensations, the wetness of his face. He's crying, shoulders spasming, a hot red core blooming between his lungs, fed by his ratcheting breath. But already he's forgotten why.

It feels, rightly, as though it's been centuries since the cannon deployed. An entire era of civilization, like children have been born, grown old and died in the time he's lain in the merciless grip of his own past. Like everyone who has ever lived has long passed. Nine centuries in twenty minutes.

With vibrating fingers, blurring vision, a state of full liminality burst open wide, pulsing around him like something alive-a twitching welter of sky and stars and smoke, ice and fire and the crawl of black decay-he resets the coordinates, runs the subtraction modification and manages the presence of mind to initiate a deployment delay. He crawls, knees buckling out from under him like an infant, stopping a moment to retch emptily on the floor before collapsing inside the transmission booth. With a hiss, the door seals behind him, and there's a countdown. Soft, digital beeping, counting imaginary clock ticks.

There's a feeling of compression, applied force, a kind of sickly inertia and a toxic taste on his tongue. Then there's the wail of another alarm, the mirrored chamber flooded with red light.

Inside his head, every swell of the mechanical bell comes with the feeling of worms tunneling, insects burrowing, a chisel being tap-tap-tapped into the prison cell of his skull, where his innumerable memories wait like caged birds ready to burst free.

A small readout screen is set into the door control panel, and it's flashing. Still pitched forward on the reflective floor, his own crimson-faced reflection staring up, he twists to one side, squinting, his eyes only adjusted enough to the glare to just make out the words.

SYSTEM FAIL. RESTARTING in 5...4...3...