Rose slithered down the steps in her bare feet, just about clutching her dressing gown around her pyjamas, and raced across the concourse to where the TARDIS wasn't. There was no sign of it parked further back, or anywhere around that she could see. She'd thought frantically that maybe he'd just moved it a bit for some reason.

She sank down onto the low wall that ran along the edge of the alley. Her limbs felt lights, as if she was going to float away.

"No," she said. "No, no, no."

Then she remembered the Doctor using the same words last night.

Oh God, why hadn't she gone with him when he suggested it? She'd known for some time that she had to hang on tight if she wanted not to end up as another accidental discard in the trail of lives the Doctor littered behind him. She'd been determined not to be another Sarah Jane.

Surely, the baby was a lifeline that ought to have kept him tethered.

Because she had thought about it, hadn't she. It had crossed her mind, more than once, afterwards, lying there in bed with him chattering nonsense. Some barely expressed thoughts along lines of, "Good job he's not an ordinary bloke, or this would be dead risky." And on those occasions, which she remembered quite clearly, she could have asked him if it was possible for him to get her pregnant. On a lazy barely conscious level, she had chosen not to.

She wasn't going to give into panic and despair. Maybe he just needed a bit of space. Like, three galaxies' worth. Or maybe he'd heard on the news last night that a spaceship had landed in Australia or something and he'd popped to the other side of the planet to take a look. Whatever, he'd be back.

She let herself back into the flat very quietly, hoping to sneak in before Jackie realised she had gone out. This never worked, ever. The flat was so small that every tiny movement could be heard anywhere, and anyway, Jackie was an expert. She confronted her in the hallways.

"What are you doing going out in your dressing gown?"

"Needed some fresh air."

"And your bare feet! For goodness' sake, Rose! Come in and get some breakfast inside you."

She had a moment of stupid hope that she would simply find the Doctor at the breakfast table, shovelling cornflakes into himself. He wasn't. Trying to hang onto her composure, Rose let her mother put down a bowl of Frosties and another mug of tea in front of her.

"Has… has the Doctor been here this morning yet?" she asked, her voice bright and brittle with affected casualness.

"No, love. I phoned up."

"You phoned him?"

"It's a her. You remember, Dr Hawthorne at the centre. She saw you when you had your tonsils out. She's nice. Oh, I don't think you've been since then, never anything wrong with you, is there. But you'll be all right with her."

"No, I don't mean the doctor at the health centre, I mean my Doctor."

"Dr Hawthorne is your doctor, as well as mine. At least, that's who I made the appointment with, they seemed all right about it. You haven't signed up with some other doctor and not told me?"

"Mum, the Doctor. Stop messing about." She was determined to keep his disappearance from her for as long as possible, just in case there was some trivial explanation for his absence, but her mum was winding her up. "You know he didn't come back here last night cos of you? I don't want all this, not now. Why can't you just be nice to him?"

"To who, love? Who are you talking about?"

"Oh, for God's sake." Rose clattered her spoon in the cereal bowl, splashing milk over the table, and stormed out of the room.

She took refuge in her room, desperate not to break down and expose what had happened. It was loyalty, and pride. She couldn't bear her mother to think badly of him, and she couldn't bear her to imagine that she'd been abandoned. Not that it was going to take long for it all to become apparent, unless he turned up very soon.

Her mother pursued her. "What's the matter now, sweetheart?"

"Nothing! Just, like I said. I wish you'd give him a break. It's like you think he doesn't have any feelings, or anything. The way you go on at him, it bothers him."

"Hang on, love. I've missed a bit here. Who are we talking about?"

She stared sullenly. "The Doctor. Who do you think."

"Which doctor, love?"

"Stop it! Are you trying to pretend he doesn't exist, or something?" She was suddenly on the verge of tears. "That's horrible! Just stop it!"

Jackie sat by her on the bed. "I don't know what I'm supposed to have done now. Honestly, I don't know why I bother. I'm trying, Rose, I really am, but how do you think I feel? You come home and tell me you're pregnant, you won't tell me who the father is, and now you're mouthing off at me for something or other and I don't have a clue who or what you're on about."

"You what?"

"You're going to need me, you know, if you're going to have any kind of life after the baby's born, since its dad doesn't seem to want to know."

"I did tell you who the father is!"

"Oh, so I suppose you didn't stand in that kitchen giving me any amount of grief last night about how it was none of my business?"

"No."

"Go on then, remind me. Who is it?"

"The Doctor, Mum. You know? Remember? The bloke I've been with for the past two years?"

"Well, this is news to me. Doctor who?"

Rose closed her eyes. Her mother wasn't faking, this was no wind-up. She was no kind of actress, her mum. Could never hide anything, it was always all out there.

"Not Dr Alluwalia from the health centre?"

"No, Mum."

"He's a nice-looking boy. Still, they can be funny, can't they – their mums usually want them to marry some girl they've picked out themselves."

"You don't remember him, do you."

"The doctor you're talking about? Rose, I had no idea you were seeing any doctor. But, well, I'm glad you've told me something at any rate. Is there a problem with him? Is he married or something?"

"He's a nine hundred year old alien from a planet that was destroyed in a huge interdimensional war," said Rose, staring ahead. "And he's gone."

She saw her mother's face harden. "We can talk about it later, when you've decided to be sensible." She paused at the door. "I phoned you in sick this morning, but you'll have to go back tomorrow. We're going to need every penny now, God help us."

"Go back where?"

"To work. If you think you're going to sit around on your bum watching telly all day like half the single mums on this estate, then you've got another think coming."

Rose said nothing, as closed her eyes again until her mother had finally shut the door.

Either her mother had flipped and lost it completely, or something beyond sinister had happened.

For some reason, she began by pulling open her underwear drawer. It was full, stuffed with a chaotic tangle of clean knickers. Surely the night before there had been about five old bra and panties sets, neatly folded by Jackie. All her current underwear was in the same sort of jumble in her bedroom in the TARDIS.

Her handbag was in the hall where she'd dropped it last night. The pregnancy test stick was where she had shoved it, in the front flap of the bag, still showing a bright blue line in both little windows. She fumbled desperately for her mobile, and scrolled down the contacts list.

The TARDIS wasn't there.

"No, no, no."

Her mother appeared in the kitchen doorway. "Oh, look at you. Come on, sweetheart. I'm sorry. Come and sit down and finish your breakfast. It'll make you feel better, I promise you."

Still dazed, Rose allowed herself to be shepherded back to the table. She stared at the food, unable to contemplate eating it. "I've already had breakfast."

"You didn't touch a thing. Now come on, you've got to look after yourself."

"Mum – do you remember what happened at Christmas?"

"Last Christmas?"

"Yeah."

"Nothing much, nothing special. We had Betty from upstairs down, cos she would've been on her own otherwise. Oh, and she spilled a whole bottle of sherry all over the carpet, we had to get the cleaners in after Boxing Day, it smelled like a trifle through there. That's all I can think of. What's this leading up to? Something to do with your mysterious doctor boyfriend?"

"You don't remember him being with us?" She decided she would leave about the bit about an alien invasion.

"No love. He wasn't. And I don't know how you had time to see him on Christmas Day, I'm sure you never left the house."

"So, I haven't been away or anything."

"Away, to where?"

"Nothing. It's OK." She flicked through the contacts list again and saw MICKEY.

She'd never deleted his name from the directory, just because he was in another universe. While her mum started clearing away the breakfast dishes, Rose hit dial and listened.

"Yeah?" It was a grunt, wary and tinged with some negative emotion, and it was Mickey's voice.

The shock was like a jolt of electricity. Rose let the phone drop onto the table, and cut the connection with a jab.

"Feel sick," she mumbled, and dashed to the bathroom.

This, for sure, was still real. She knelt on the carpeted floor of the bathroom, inhaling the smell of bleach and lavender, too scared for tears but heaving with nausea. Throwing up had given her no relief.

Somehow, she had ended up in her life as it would have been if she'd never met the Doctor. Was that right? How could it be? If she hadn't met the Doctor that day, in the basement of Hendricks, the Autons would have killed her. Well, maybe this was the alternative universe where she'd not gone back into the story at all that night to collect the lottery money. She would have headed out home with the other girls, got on the bus home with a bag of chips, and learned about the explosion at the story later, on the telly.

Was that right? But how about last Christmas? There had been a Sycorax invasion and everyone in London, at least, had experienced it first hand. Every Londoner's memories of last Christmas were surely dominated by the giant ship hovering over the city. Even her mum couldn't be so focussed on the trivial that Betty from upstair's sherry-spilling could be remembered as the major event of the day.

But the baby, the Doctor's baby – it was still there. She was still pregnant, no doubt about that.

Nightmarish speculations began to crowd in on her. What if she'd somehow swapped consciousness with an alternative universe version of herself, one who hadn't met the Doctor that day. Maybe the whole Sycorax invasion had been brought into being by her subsequent involvement with the Doctor, through some complex chain of cosmic causality. And this Rose had continued to live her mundane life, and had simply got herself up the duff by some sleazy bloke she knew Jackie would disapprove of. She could be lying here with some stranger's baby inside her.

She retched again, the last dregs of breakfast.

"No. No, no, no."

She clamped her hand over her lower abdomen.

"Oh dear," said her mother.

Rose cursed herself for forgetting to lock the door, again.

"You have got it bad. Still, they say, the sicker you are, the safer the baby."

"Mum. I do want a scan. I – I – want to make sure the baby's all right."

Fresh air made her feel better physically. First she returned to where the TARDIS wasn't, and walked carefully around the patch of ground to see if she could spot any flattening of the grass or any signs that might suggest a moderately heavy transdimensional spaceship had been standing there the day before. Then she flipped open her phone again and, pacing restlessly, hit dial on Mickey's name.

The phone at the other end burred several times before his voice answered. "What do you want, Rose? What are you calling me for?"

"I need to see you. Where are you?"

There was a long pause. "Where I usually am at half nine in the morning. At work."

"At Bob's garage?"

"Yeah, where else."

"Can I meet you there?"

Another pause. "At the caff. Look, what's this about?"

"I'll tell you when I see you." She snapped the phone shut.

There was a small greasy-spoon café at the corner of the street where Bob's garage was, the place where Mickey had worked between leaving school and joining them on the TARDIS. It made sense that in a world where the Doctor hadn't come into their lives, he would still be there. He certainly hadn't been going anywhere else. She remembered that was one of the things that had vaguely frustrated her about him when they had been going out, that the height of his ambition was one day, maybe, to have his own garage.

He was already waiting for her at one of the formica tables, wearing a wary, sullen expression.

Her heart turned over as she closed the café door with a jangle. She had never expected to see him again, and she had no idea on what terms they were meeting now. Clearly there had been some argument between them, but what the status of their relationship was supposed to be, she could only guess.

"I've got fifteen minutes," he said. "Took an early tea break."

"OK." She sat opposite him. "Mickey, you're going to think I'm off on one, all right, but just listen for a bit. Does the Doctor or the TARDIS mean anything to you? The Cybermen?"

"Are they new bands, or something?"

"So that's a no, then. All right. This is going to sound even weirder. You and me, what happened?"

He scowled and broke eye contact. "You tell me, I still don't understand it."

"We've split up, yeah?"

"What's this all about?"

"Hang on, I said it was going to sound like I was off my trolley."

"Well, that's what I think you were. There was no reason that I could make sense of. It's not as if you had another bloke or anything, not that you'd tell me anyway, and if there was I'd've heard." He glanced up at her, a quick hurt look.

"OK… when was this?"

"You when it was. Stop messing about."

"But just imagine for a moment that I don't, Mickey. That I've lost my memory or something."

"What is this?"

"Just tell me."

"Almost a year ago. This time last year."

She looked at the window, where sleet was spitting against the glass with its faded stencilled letters spelling AHMED'S CAFÉ backwards. So, a little later than she had finally dumped Mickey in her own reality, but not by much. If that had any significance or bearing on the situation, she had no idea.

Fear began to take hold again. The surroundings were depressing, and despite the weather she felt too hot, and Mickey's hurt and hostility grated against her raw nerves.

"You know it's too late if you've had a change of heart," said Mickey. "I'm happy with Trish. There's no going back. No way am I going to do to her what you did to me."

Oh, Trisha Delaney. Rose saw at once that he wasn't particularly happy with her.

"It's OK, I've got someone else as well."

"So what did you want to see me about, then?"

She was stumped. Because she'd got so used to Mickey being on the inside of the team, she'd had some deep-rooted idea that she'd be able to tell him everything and he'd be full of suggestions. But this was the old Mickey, who was like a stranger now. The old Mickey, untouched by the direct experience of everything the Doctor had brought into their lives, simply wouldn't understand or want to listen if she tried to explain. "Can I go round and use your computer?" she blurted out. "I want to check something on the Internet."

"I suppose. Trish would have a fit if she caught you there, though."

"Is she likely to be around there now?"

"No, she's at work."

So Trisha was living with him. Peversely, Rose felt a pang.

Mickey fished in his pockets and slapped a set of keys on the table between them. "On you go. Just don't leave anything lying about, or she'll notice."

Mickey's flat didn't smell right. Instead of an atmosphere of unwashed socks, unemptied bins and open beer cans, there was a sickly odour of cleaning fluid and room perfume. It was unusually tidy, and there were pastel cushions on the sofa, a new rug on the living room floor, and prints of cute animals on the walls.

Curious, Rose glanced into the kitchen. Every surface and appliance gleamed. There was a tree of matching bright mugs and a floral-printed kitchen roll on a mounted holder.

The bed had a patchwork throw and an arrangement of embroidered pillows. Trisha Delaney had evidently got her feet well under the Ikea coffee table.

Even the computer looked like it had been polished. Carefully, almost worried about leaving smudges on the mouse mat, Rose turned on the system and got up a search engine.

She realised her hands were shaking as she typed in THE DOCTOR. This was the moment of truth, really.

Pages and pages of links about hospitals and medical doctors came back. No links to the many sites speculating about the mysterious traveller who appeared and disappeared throughout history.

She tried the names Clive and Elton Pope. Clive, who appeared to be alive and well, ran a web site about UFO sightings over Britain and the UK Government's involvement in the 1969 Moon Landing Conspiracy. She got one hit for Elton, a bad picture of an amateur rock band from a local newspaper. It was him though, dated a month ago. His arm was around a girl she just about recognised as Ursula.

Death hadn't come to these people. The Doctor hadn't been here.

It wasn't just that he herself hadn't met him. He was gone.

"But you can go back in time to any point in history, or forward. Why can't you go back to before the war, when there were other Time Lords?" She had asked that once, long ago, when she had still been fairly clueless, and when the Doctor had still been as he used to be.

He'd answered grimly, looking away from her. "Think I hadn't thought of that?"

"No… I was just asking why you can't. Cos it wouldn't be crossing your own timeline or anything if you went back to before you were even born."

"The Time War was just what it sounds like, a war across all space, all time, all dimensions, all realities. You lose, you're gone. Phut." He snapped his fingers. "My people were removed from the fabric of space/time. They no longer ever existed."

"But you… what about you – why are you still here?"

He said nothing, and turned further away, and carried on stabbing at the guts of the TARDIS through an open floor panel.

Rose remembered that she had hovered in desperate awkwardness, regretting having said anything at all, wondering whether to apologise but sensing that this would be to wade deeper into the mire. In the end she'd slunk away and that had been the end of that conversation, forever. She'd felt, ever after, that the Time War was a taboo topic and anything to do with his past was hedged around with no-go warning signs. That was why she hadn't asked him anything about his children, even though she was ravenously curious.

He didn't do the brooding silences of his old self any more, but she was still afraid of his dark flipside.

Could he have been erased from time and space somehow, like the rest of the Time Lords? But how, and why?

No, it didn't make sense. His homeworld had been destroyed and all his people killed, but those who had been touched by them still remembered them. She was sure of that. Jack had known about the Time Lords, even though he'd thought they were just a legend. And now, it seemed that she was the only one who had any memory of the Doctor's existence.

Was it the baby? Was it a lifeline in a different way from how she'd imagined this morning? Was it keeping her tied to reality, when the rest of the universe had been warped out of shape by some bizarre catastrophe?

She began to feel nauseous again as she reached the flats, and sat down on the bottom step for a rest. She missed Jack, suddenly and intensely. She'd only ever half-bought the Doctor's claim that he'd asked to stay behind on Gamestation and help rebuild after the Dalek invasion. He'd been another accidental discard, she reckoned glumly, and the Doctor had never mentioned him again.

And she hadn't cared. She'd more or less known the Doctor was more or less lying about Jack's departure, and she'd gone along with it because it was all change anyway and she was alone with the Doctor again and things were moving on rapidly at that point. Looking back, Jack had been this huge horny catalyst in her relationship with the Doctor, somehow clarifying things in his own libidinous terms, giving her the impetus to finish with Mickey and setting a clock ticking on a countdown to consummation. He was just so outrageous and upfront, he had brought sex on board the TARDIS even though she personally wouldn't have touched him with a bargepole once she learned he swung both ways.

But now, she missed him. He'd know what to do. She needed help, she needed someone to talk to.

Jackie was watching television when Rose came back in. "Feeling better?"

"Yeah, the walk did me good."

"I'll get some lunch on then. Will sandwiches be OK?"

"That would be great," said Rose, realising that despite everything, she had swung from sickness to galloping hunger. She felt like her body was as much at odds with her as the rest of reality.

"Sit yourself down then, and I'll bring you something through. It's interesting, this – she's doing a programme about what's going on in Chinese orphanages. Terrible."

Blankly, Rose stared at the screen.

"Mao Li is eighteen months old," the presenter was saying, lifting up a tiny, apathetic scrap of baby from a bare cot. "She's just one of the two hundred baby girls abandoned at birth every week in this province of North-West China alone."

The camera panned in for a close-up of the presenter, gazing tenderly at the wizened monkey face of the underweight child. At the back of Rose's brain, it had registered that the voice was familiar. With a shock of surprise, she recognised Sarah Jane Smith.

"Mao Li weighs around what a healthy child should weigh at six months." The presenter looked straight into the camera. It was definitely her. "Without proper care, she is going to die soon. And there are thousands like her all over China."

"On second thoughts, don't watch that," said Jackie from the doorway, switching the television off with the remote. "That's not the sort of thing you want to be upsetting yourself with in your condition."

"Mum! Do you know who that was?"

"Of course I know who that was, that's Sarah Jane Smith."

"You've heard of her, then?"

Her mother stared at her. "Everyone's heard of her." She shook her head. "Where have you been?"

"Good question," said Rose, to herself, as her mother went back through to the kitchen.

She found her mobile and scrolled the contacts.

This time, she wasn't disappointed. The name and number that she had programmed in a few months ago, at Sarah Jane's urging, and had always hoped she would never have to use.