Even in the midst of her terror, Vida wondered if she was going barking mad. She was being washed out of her own offices, towed along like driftwood in the rapids. It was just too surreal.

The main door had been left open. The steps, she thought in a panic, I'll break my back. But the water seemed to solidify beneath her, made a kind of cushion as she slipped down on to the pavement.

She screamed, kicked and smashed at the water, but on it flowed down the street, carrying her away. Will it stop at the traffic lights? She wondered distantly, trying to impose some kind of logic on her situation. Then she saw the gaping hole ahead. A manhole cover stood propped against a parked car. Oh, please, this isn't happening.

Helplessly, Vida plunged down into the blackness of the sewer. She heard the splash but felt nothing. She knew the sewers carried rain-water as well as waste in a combined system. And where did these overflow channels lead?

Where else? Out into the Thames. . .

The water coiled round her like a cold cocoon, protecting her as it rushed her away. Is this what happened to you, Andrew? Her mind fixed on the thought in the inky darkness. She was picking up speed, and tears began to ball in her throat. Maybe I'll see you soon.

Rose and Peter ran out into the middle of the road and stared all around.

"Vida?" Peter yelled. But the road was deserted: no trails, no signs of life at all. The street was quiet and empty.

The distant sirens sounded louder out here. They made a good soundtrack for her emotions. Where the hell had Vida gone? How could she just vanish? Rose and Peter started running again, in case they could maybe catch her up.

It might have been a lost cause, but if truth were told Rose couldn't face Keisha and Mickey right now. Didn't even want to think about that. Swanning about on alien planets, she felt she had outgrown her former life; and yet this spiteful little home truth had grabbed her by the scruff of the neck and dumped her right back into the old days.

How could they. . . ?

She shook her head, kept on running, pushed herself harder as she and Peter raced down the street. Vida needed help and fast. If the water aliens had meant to kill her, they could have got her back in the building. So they must need her alive for some reason. But why?

The blare of sirens was getting louder. As they neared the bottom of the road, an ambulance and a large police van screeched from out of a side street. It stood to reason they were heading for the river. And since they were too. . .

The vehicles slowed down at the red traffic lights, checking the roads were clear before speeding on their way. Rose glanced at Peter to check he had the same idea in mind before they seized the moment and ran up behind the police van. Steeling themselves, they jumped up lightly on to the back bumper and each gripped hold of one of the handles in the blank double doors.

"Great, great plan, Rose," Rose muttered. But this was a matter of life and death. With luck they would stop just round the corner, at the sight of a blonde woman being carted down the street by a runaway puddle. "Hang in there, girl," She murmured, both to Vida and to herself.

Then, clinging on for dear life, they found themselves hitching a ride riverwards.

The Doctor struggled up from the lab floor, but it felt more like he was pushing himself up from some dark, distant sea bed. He wasn't having this.

"I'm. . . not. . . like. . . humans," He spat, pushing out the words with the last of his breath. "You. . . can't. . . have. . . me."

The water began to lose its strong taste. His mind began to clear.

He clamped his eyes shut, felt water squeeze out, nodded furiously, willing himself on. "Get out of me," He shouted, and at last he could breathe again. "Out!" He roared.

His face and clothes were dry, as if the attack had never happened.

He rushed to the sink, but that was dry too. "Where are you?" He yelled, turning on the taps. The water came out under enormous pressure, splashed out of the sink, soaked him properly this time, all over his waist and trousers.

"Doctor!"

"Mickey?" The Doctor spun about to face him, glanced down. "OK, big wet patch on the trousers there. Looks dodgy, I know, but it's not what you think."

"We were attacked," Mickey panted. "These jokers in fancy dress, they came out of the water."

"They did? Oh. Yeah. I'll bet they did." The Doctor ran over to check on him.

"Killing several birds with one wet stone. Reabsorb the water sample, try to suss me out since I'm not a local, and –"

"They've taken Vida," Said Mickey. "Just slooshed her away in a load of water, right out of the door."

"Rose and Peter went after her," Keisha added, cowering back out in the corridor.

"Did they?" The Doctor winced. "That wasn't very wise. Brave and adorable, yes, but not wise."

Mickey shot a look at Keisha.

"Can't say I blame Rose for not hanging round."

"You just did," The Doctor said vaguely. "Come on, think. Why would they take Vida?"

"How are we supposed to know what a puddle wants to do with its life?" Then Mickey froze. "Hang on. This vice admiral bloke she was supposed to meet, 'cause her boss has gone missing. If she can't meet him, she can't blab, can she – and Crayshaw gets off the hook."

"I don't think Crayshaw is too worried about some bigwig rapping his knuckles. But bigwigs do have their uses. . . "

"God, we were gonna tell you," Said Mickey. "Crayshaw's old – we're talking 250 years old. He's in the naval records, same bloke. Drowned at sea."

"The aliens got him," Said Keisha fearfully. "But how can he be so ancient?"

"The Doctor didn't look surprised in the slightest. "The human body is 70 per cent water, and salt's a natural preservative. Throw in some alien biochemistry. . . "

"He was wearing shades when we saw him," Mickey confirmed. "He must have pearls for eyes, like the ones who whacked me. He's one of them."

"Let's get to the Mickeymobile," The Doctor said. "We need to go to Stanchion House. These things will have taken Vida there."

"You don't know that."

"I bet you anything they have! How much do you wanna bet? Anything! Ten, twenty, fifty. . . a quid?"

Mickey shook his head wearily.

"So, what're we gonna do?"

"Break in, of course!"

"But there'll be soldiers everywhere!"

"I want to go back home," Said Keisha quietly. "I can't deal with this. Please take me back so I can wait for my mum."

Mickey glared at her.

"First we need to find Rose And Peter."

"Shouldn't take long," Said the Doctor brightly. "We'll grab them on the way. They can't have got far!"

"Omigod, omigod, omigod." Rose was still clinging on to the back of the police van. She kept wanting to bang on the doors to make it stop, but didn't dare let go of the handles. Peter was stood next to her, also struggling to maintain his balance. Though his grip was improved by digging his claws into the metalwork of the van. Some poor police officer was going to get very confused by the puncture marks.

To Rose this had to rank as one of the dumbest things she'd ever done. Her heart was throbbing faster than the engine; the ground was blurring by – they had to be doing forty or fifty miles per hour around these streets. There was no sign of Vida anywhere and she had no feeling left in her fingers. Every time they took a corner her arms burned with the effort of keeping her balance.

But finally the van screeched to a halt near the river. Rose unhooked her fingers. She would have tumbling to the ground with all the grace of a cartoon character who's just run into a brick wall had Peter not got down first and helped her step off. Both aching everywhere, they scrambled underneath the vehicle, just as the back doors were flung open and the boys and girls in blue piled out. Thankfully they hadn't noticed the claw marks Peter had left behind.

"The driver was mad," Said someone, a few feet away.

"Tell me about it," Rose muttered. She and Peter peered out from beneath the van and saw a police officer being comforted by a female colleague.

"Had to get to her sister, she said. Nothing else mattered." He shook his head. "She ran the blockade and then. . . "

"Come on," Peter whispered to Rose before they pulled themselves from under the van and hurried for the cover of a nearby ambulance. But halfway across They got what they were talking about, and a sick feeling gripped Rose's stomach.

The tail end of a double-decker bus was sticking out from the Thames's dark waters. Little police boats circled it like sharks. A huge hole gaped in the wall beside the river where it had ploughed through.

"What's happening?" The policeman went on. "As fast as we block their way to the river, they break through."

The woman squeezed his shoulder.

"Leave it to the soldier-boys. If they're so keen to deal with it, let them."

Yeah, that's the spirit, thought Rose darkly. She followed Peter in flitting between the parked vehicles, Peter's night vision and the blue flashes from the vehicle's siren lights the only way to know where she was going.

They had to reach the river's edge without being seen – easier said than done, given the number of coppers and squaddies roaming about, arguing over who did what. Then Rose spirits rose a little as she recognised one of the boats moored to the wharf. Or rather the big tool kit and blanket on its deck, which were clearly PC Fraser's. Better still, there was no sign of anyone about. If he could only help her find Vida before it was too late. . .

"We gotta go to that boat there," She pointed it out to Peter. "There's someone who might be able to help."

They hurried down the steps to the small jetty. It was darker down here. The moon was just a faint crescent half-buried by dark clouds.

By its feeble light, Rose was struggling to see where she was going and bumped into Peter's back when he suddenly came to a halt. She knew something was ahead of them yet it took a moment to spot the twitching bodies of a pair of soldiers on the jetty, clutching at their throats, mouthing in silent gasps.

So much for no one about. Hopefully they would be found soon by a passing patrol. Rose felt the hairs standing up on the back of her neck

"Where's this person you wanna meet?" Peter asked over his shoulder. Rose turned to the boat.

"PC Fraser?" She called. "You there?"

A dark shape appeared from inside the cabin, crossed the deck. "Hello?" Rose said uncertainly. "Fraser, you've seen someone, haven't you?"

"My mate, Fisky." It was Fraser all right. She couldn't see him, but his voice sounded hoarse and strained. "He couldn't tell me where the bodies were, 'cause he'd gone to join them."

Rose and Peter walked steadily towards him.

"Let's talk about this, yeah?" Peter asked. "A sit down? Nice cuppa tea maybe?" He could see the all too familiar lost yet determined expression seen on all those wishing to join those of the Ascendent.

"He was my mate." Fraser turned, ducked out of sight. "I've got to help him."

The sound of the hefty splash tore through Rose like an explosion.

"No!" She shouted, as she and Peter bundled on to the boat. "Whatever you saw, it wasn't him!"

They peered over the rail. "Where is he?" It was so dark she couldn't see a thing.

"He's gone, surely he couldn't have gone under already..." Peter said in shock as he failed to spot the man's form in or under the water.

Then a blinding light bleached out the scene, as powerful floodlights were trained on the sunken bus from the river's edge. Rose flinched, lost her balance. Plunged head-first into the freezing river.

She turned a somersault in the water, kicked up with both legs to break the surface. Gasping and choking, she pushed her hair from her eyes, tried to blink away the water. This is the Thames. What the hell am I gonna catch from being in here?

Or what's gonna catch me?

"Rose!" Peter's voice penetrated through the darkness. One moment she'd been stood besides him then the next thing he knew she was struggling in the water below him. "Grab my hand!" He shouted as he bent down over the railing as far as he could and tried to reach for her.

But as Rose made for him, her arm reaching out for his, she felt something tug at her trainer. It pulled her down beneath the surface before she could draw breath. She kicked out, tried to free herself, but it was no good, she was being dragged down. Something bumped into her back –

Peter? Yeah, it must be Peter coming to help her – he would have seen her been pulled under. . .

Something sharp punctured the back of her neck.

Rose flailed furiously in the freezing water. But her lungs were already bursting, and a blood-red light was pressing in on her vision.

At first she thought it was in her head. Then she realised a shifting landscape was resolving itself from the gloom, that vague and horrible shadows were drifting at a distance, all around her. Another burst of red light. Then they all scattered, even the force on her neck and foot left. Something had disturbed them as the surface rippled overhead. A very odd yet peaceful stillness descended.

Rose knew it was Peter this time. His strong arms wrapped themselves securely around her waist from behind before beginning to pull her upwards. He'd dived in the minute he'd seen her get pulled under and had fired a shot from his gun to scatter the shadowy creatures he'd seen enveloping her. Now they were heading back to the surface, back to dry land and safety.

The chaos arrived as quickly as it had left. The creatures, initially scared off by the bolt of energy Peter's gun had fired, now realised there was no real threat. This time they would finish the job and take two bodies in one go for their effort.

When Rose felt Peter's grip wretch away from her she began to panic. He'd disappeared in the blink of an eye. Had the creatures got him too? Terrified, she fought hard, and finally she kicked free of whatever it was now trying to dragging her under. Her clothes were weighing her down but she swam upwards, ignoring the steady throbbing at the base of her skull. She thought of nothing but propelling herself upwards, away from the red light, away from the things. She had no breath left, every movement hurt and dizzied her, but somehow she kept going.

She had to get away. . .

For Mickey, the night did not improve.

He drove the Doctor and Keisha around for hours but there was no sign of Rose or Peter or Vida anywhere. And all the main roads down near the river were blocked off with barricades and soldiers, so they couldn't even get to the most likely places. He drove past a hospital in Westminster and wondered if he should go in and ask about new arrivals. But stuff was clearly kicking off there. People were swarming round the entrance like flies round rotten fruit. The Doctor wasted no time poking his nose in and found that the number of dehydrated people was on the increase – but no sign of Rose, Peter and Vida.

"Our ghosts are keeping busy. But what do they want, besides a quick glug?" He turned to Keisha. "You haven't seen Jay again?"

"No," She said, and sounded so sad about it. She kept quiet for the rest of the ride. Shame she couldn't have watched her mouth when it really mattered. Don't go over that again, Mickey told himself.

There was a definite uneasy atmosphere brewing in the city, he could feel it. The endless sirens, people spilling in and out of hospitals, wanting answers, getting nothing. And blocking off the river only fed the rumours of disappearing people. The sight of so many soldiers on the streets didn't help matters – it implied the police couldn't cope, that some sort of national emergency was in progress. But listening to the news there was no statement, no announcement. No one knew what the emergency actually was, just that it was going on around them.

"Even if we could find somewhere to look how do we know they'll be there?" Mickey eventually asked. Rose's and Peter's mobiles had failed to be answered by their owners and it wasn't as if they had know themselves where a pool of alien water would lead them. "Isn't there some way off tracking them?"

"Ordinarily I'd scan for alien life, it'd pick up on Peter in a jiffy but..." The Doctor began.

"What? Peter's an alien?" Life flooded back into Keisha alongside the shock and horror. The Doctor and Mickey chose to ignore her.

"Too many aliens running about, or should I say flooding about." His smile at the joke was not joined by Mickey's and Keisha's. "No? Flooding about? Get it?" He tried to prompt before clearing his throat as they drove on in a awkward silence. "Oh!" Mickey nearly crashed the car as the Doctor sat bolt upright in his seat.

"What?"

"Peter's communicator! It has a low level signal tracker! Easy and unique enough to pick up on." The Doctor grinned broadly as he brought out the sonic screwdriver. After a bit of fine tuning it's blue light began to gently pulse as it started relaying Peter's location.

They all paused when they saw the sight of the double-decker bus floating in the river. The police operation had died down to the level that showed it was no longer a rescue mission, rather a salvage mission.

Still they had to be careful as they sneaked past an headed for the jetty the sonic screwdriver was pointing them too. "Rose? Peter?" The Doctor called out into the darkness. Dawn was beginning to break but it was still impossible to see much.

"Are you sure they're here? Maybe that thing's busted" Keisha stated, pointing at the sonic screwdriver. Again they ignored her.

"Is it telling you where to go next?" Mickey asked the Doctor.

"It's telling me Peter's here." The Doctor hadn't meant to snap but his worry was mounting. Peter's communicator was here and it never left his arm. Yet there was no response from either him or Rose, if she was still with him that was.

"I've got a torch in my car. Back in a minute." Once Mickey had left Keisha took her chance.

"You know Rose had never said who you are? All this time she's been gone and all I've ever been told is 'he's just the Doctor'." The Doctor wasn't really in the mood to try and explain or make up a cover story. Instead he focused on fiddling with the sonic screwdriver so that it would hopefully give him more information. "In the car too, you said you'd scan for alien life, that Peter would come up. He's an alien isn't he?"

"Keisha..."

"What kind? 'cause he looks human,"

"Keisha..."

"I'm surprised Rose never mentioned..."

"Enough!" The Doctor tolerant finally snapped. "I'm trying to find him and your best friend here, the least you could do is give me the peace to do it." Keisha was use to being shouted at and so was more offended than hurt.

"Some best friend, clearing off for a year without so much as a word" She muttered as Mickey reappeared with his torch.

"Anything?" He asked as he switched it on and began scanning the jetty and moored boats with the beam of light.

"Peter's an alien. Did you know that?" Mickey couldn't tell if she was finding it a joke or was being deadly serious. He chose the safe option and ignored her.

"I've been scanning but it's still saying he's here" The Doctor muttered, still fiddling with the sonic screwdriver.

"Doctor" Mickey said quietly, his torch beam resting upon a small police patrol boat. His tone and Keisha's frightened shriek filled the Doctor with instant dread as he looked up.

The back of the boat had been reduced to a chaotic tangle of torn metal by the set of claws that had sunk into it. Frantic and desperate in their position and depth they told the whole story to the Doctor. The plunging into the water, the frantic scramble to get back out again as Peter tried to escape whatever horror had been lurking under the dark surface.

"There's...there's blood," Keisha stammered. So there was. A small trail of brown stained the paintwork, unmistakably dried blood. It led from the railing down to the water. Hang on? The railing? Where the safety of the deck was?

Taking the torch off Mickey, the Doctor titled it up ever so slight.

Peter was led on his left hand side, curled up in a ball, his hand where it was when he'd passed out, trying to cover a patch of oozing blood from spilling out his neck that had leaked out and pooled around his head.

"Peter!" The Doctor almost slipping off the jetty in his rush to reach his companion. Careful not to tread in his blood he knelt down besides him and gently felt for a pulse. His sigh of relief was enough to reassure Mickey and Keisha that he was indeed alive.

Deathly pale from the blood loss and colder to the touch, he was oblivious to the world but alive. Up close the Doctor could see the offending and ugly puncture wound in his neck. A quick scan with the sonic screwdriver told him it was the same alien source found in Rose's and Keisha's eyes and blood. Much to his relief it also showed the wound was healing well enough on it's own.

Still he'd been lying here - hours going on his dryness - losing blood and dealing with whatever poisons the creature dealt out. All on his own.

"What did it?" Mickey asked. He tentatively climbed onto the boat and stood just behind the Doctor.

"Same thing we're hunting."

"Will he be all right?" The Doctor gentle stroked the side of Peter's head, hoping it would get through the darkness of unconsciousness and comfort and reassure him.

"We need to get him somewhere safe, let him recover."

"What about Rose?" Keisha suddenly asked. She'd been watching from the jetty. "Wasn't she with him?" The Doctor and Mickey glanced at one another. It was obvious she was no longer here, but had she been?"

"Let's hope not." The Doctor said.

They were back on the estate just as the first rays of sunlight were nearing the horizon.

Mickey kept wishing and wishing in his head that they would find Rose safe and sound at Jackie's place. They had to find her, and she had to be OK. The thought that something bad had happened to her straight after hearing about that night – the night he couldn't even remember. . .

Peter had not yet come too but he regained a little colour as the wound slowly stopped bleeding and started to shrink. Still he was far from recovered. Lying on the car's back seat – Keisha grudgingly but uncomplainingly having to share the front passenger seat with the Doctor – the Doctor had wrapped him up in his large coat before they'd set off and had regularly leaned back and checked his condition with a quick scan with the sonic screwdriver during the journey.

But before they moved him anywhere the Doctor and Mickey had jointly decided it best Keisha should be returned home. At the very least it would give Peter further time and peace to recuperate.

Mickey walked her up the stairs to her flat in silence, while the Doctor had stayed with Peter in the car. Keisha fumbled for her keys.

"I didn't know this was gonna happen,'" She said, pushing open the door. "How could I have known?"

Mickey shrugged.

"Whatever, I'm going to help the Doctor get Peter to Jackie's.'

She nodded.

"I hope he'll be ok," She paused. "But I need to find Rose too, Mickey. I've gotta talk to her."

"Ain't you said enough?"

"I've got to. 'Cause. . . " Keisha took a deep breath. "'Cause. . . it never happened."

He frowned.

"What?"

"Us. That night." She didn't look at him. "It was me who tried it on, not you. But you didn't want to know. You crashed out, and I let you think we'd. . . "

"You made it up?" Mickey stared at her, conflicted, wanting to believe her but not daring to let himself off the hook. "Serious?"

"I ain't used to it, Mickey. Rejection, I mean. Getting boys is the one thing I can do."

"But Rose is your mate. One of your best mates."

"I know. I ain't proud of what I –"

"Which is why you put the blame on me, " He realised.

"I know you never liked me. That's sort of why I wanted you." She snorted. "I know it was stupid, but you kept going on about how she'd pushed off and left us all, how she didn't care and was never coming back, and that hurt me, Mickey, just like it hurt you. That she could just go off like that."

He shook his head, incredulous.

"And what, you wanted to get back at her by copping off with me?"

She looked at him at last.

"I dunno what I wanted."

"But you knew it made you feel like dirt," Said Mickey. "Which is why you had to punish me for what never happened." He could feel his anger building. "The bricks through the window, the stories you spread, the blokes you got to rough me up – all 'cause of nothing?"

Keisha walked over to the cluttered dining table. "So how come you told Rose that rubbish?"

She ignored him. "How come?"

"'Cause I ain't forgiven her, Mickey," She snapped, slamming down her fist. "She's my mate and I love her, but she's changed. She's like a different person now she's with that Doctor."

"And you wonder why you drive people away!"

"You can see she's changed. You know it."

"Maybe I do," He said. "But I still love her, whoever she is." He slumped down on her sofa. He should have felt elated, he supposed, or mad with anger.

But he just felt tired. Tired and scared, because that nagging voice that kept telling him he would never see Rose again was growing louder and louder.

He jumped as the tinny little tune of a mobile phone broke the heavy silence. "That ain't yours, is it?"

"Like it would be," She said. "Oh, God. It must be that old woman's."

"Her name was Anne," Said Mickey, and picked up the chunky hand-set. "Do I answer?"

"I dunno."

He bottled it, and let the phone ring on. But as the tune stopped dead, he noticed the display: 23 MISSED CALLS.

"Someone's off their head with worry," He murmured. She had a stack of voicemails waiting, and he found himself dialling the answer-phone number as prompted.

"You have fourteen new messages. First message:. . . "

A woman's voice spoke softly in his ear.

"Anne? It's your sister, I've just seen you but. . . Oh, Anne, it can't be you, can it? You can't be under the Thames."

Mickey felt the mother of all chills mess with his spine, put the mobile on speakerphone. "It's a trick, it must be," Anne's sister went on, halting, clearly trying not to cry. "Tell me it's a trick, Anne. When you get this, tell me you're OK." She paused, then rang off.

"Anne's one of them too." He looked at Keisha. "She's turned into a ghost-thing like Jay."

"She can't have," Said Keisha. "She was never on the Ascendant. How –"

A man's voice came on the line next, reedy, agitated:

Anne, it's David. The weirdest thing just happened, I saw you – thought I saw you, anyway, in my front room – and you told me you. . . Well, it's stupid, I know, but it was so real. I can't get hold of you at home. Please, when you get this, call and let me know you're OK." A pause. "See, this image I saw, it said something about the drowned, and I know you're still raw from poor James going –"

Mickey killed the call.

"The same thing's happening. They drown, they come back, they trick more people into drowning. First the ship's crew, haunting the people they love. Then those people haunt the people they love. Sort of like a cycle – don't you get it? That's why London's so mad tonight – the effect's spreading. It's gonna keep spreading!" He stood up. "I've got to go tell the Doctor, let him hear this."

But Keisha was staring past him, at the doorway. She was trembling.

He turned. It felt as if he was moving in slow motion.

Rose was standing there. Large as life, picked out in pale colour.

She looked scared half to death and dripping wet.

"Oh, Mickey, Keish, you've got to help me," She said, her lips out of synch with the words. "Say you'll help me." She gave them an encouraging smile and a trickle of water ran from her nose. "Help me before the feast."