Rose perched on the rim of the metal toilet and watched the second blue line grow solid. If she'd been imagining that she felt sick before, there was no doubt that she did now – as soon as the whisper of a suggestion of a line appeared in the little window, all the half-joking ideas of the past few weeks solidified into certainty and fear.

It was so hard keeping track, in the TARDIS. She'd completely lost any sense of how long she had been aboard or what day of the week it was. Every day was new, and different. It had been impossible to reassure herself when she'd begun to suspect, but it had been pretty difficult to take that suspicion seriously, either.

She was hopeless. She had completely lost it. She had no idea where she was. It was only when the Numidian tea that she'd got so keen on had started to taste so disgusting it had made her puke, that she decided she had to know.

Trouble was, there wasn't exactly a stack of Clearblue in the TARDIS medical cabinet. She'd had to pretend she wanted to go home – no reason – just to see her mum, and then she'd had to make an excuse to go shopping on her own first of all. She'd sent the Doctor on ahead to her mum's, and taken a bus to the Archway Shopping Centre. No way was she going down to the chemist's on the parade, where Doreen the pharmacist's assistant would tell the whole estate that Rose Tyler had bought a pregnancy test.

And she hadn't been able to wait until she got home to do it. The box said two minutes, so she went into the niffy public lavs next to the centre and did it there and then. Shut in a metallic cubicle, she stared at her future.

It was a gritty, whippy day – not raining, but grey as the concrete of the pavement and walls. Rose hurried up the three outside staircases to what had once been her home.

The atmosphere in the flat hit her as soon as she opened the door. Her mother was in the kitchen with a stiff, huffy back, clattering cups, and the Doctor was sprawled in his usual place on the sofa, staring at a daytime TV show with a brooding expression. As soon as she stepped into the hallway, her mother thudded down the kettle and ran to her.

"There you are. Oh, thank God."

"Yeah, here I am, Mum – what's the matter? We haven't been gone a year again, have we?" She was squashed in a bear hug.

"No, but when he turned up at the door without you – "

"Told you," said the Doctor.

"That was my fault, Mum –I just wanted to go off and do a bit of shopping, that was all."

"Well, I thought you were dead."

"I told you she wasn't," said the Doctor, changing channels with the remote. "But would she believe me?"

"Mum, don't be silly."

"Silly? I know the kind of life you lead. Every night, I lie awake worrying what the hell might be happening to you. One day, he is going to turn up alone and tell me that you're not coming back, ever."

The Doctor caught her eye and shrugged at her, but Rose was rattled. She scowled back and put down her bag.

"Oh, come on in and sit down," said Jackie. "I haven't got anything in to eat, though."

"Oi." Rose prodded the Doctor. "Make yourself useful and go and get us something from the chippie."

For once, the Doctor seemed to appreciate immediately that his absence would be a good thing. He unfurled himself willingly enough, accepted the £20 note that Rose offered him – he never had money of his own, none that you could spend anyway – and darted out.

Jackie sighed and shook her head at the door.

"Mum…"

"What is it, love?"

Suddenly, Rose realised that she was close to tears. "Mum, I've got a problem. I'm pregnant."

"Oh – my – God. Rose!"

Her mother's entirely predictable shock and displeasure felt, nonetheless, like a slap.

"Is it his?" Jackie jerked her head towards the door.

"Yeah. Of course!"

"Well, it's not that long since you had Mickey on that ship with you."

"Mum, I finished with Mickey over a year ago! When he was travelling with us, we were just friends."

"How do I know what's going on? It's not as if you ever tell me. Oh my God, Rose, he's an alien!"

"I know that."

"It could have two heads or something!"

"Don't be stupid, he doesn't have two heads, does he."

"No, but he does have two hearts. You told me that. What else is different?"

"Nothing. I don't know."

"How could you be so stupid?"

"I didn't know it could happen! I thought it would be impossible!"

"And what's he got to say for himself?"

"I haven't told him yet. I only just did the test. It's why I came home." She could feel the tears rising through her voice.

Jackie's expression softened, and she pulled her into a hug. "Don't cry, love. We'll sort something out, don't you worry."

Rose pressed her face into her mother's neck, inhaling perfume and fabric conditioner, deodorant and shampoo. "Not that long we got stuck somewhere, we thought we'd lost the TARDIS and we were never going to be able to leave. I said if we were going to be stranded, we should get a place together. He went all funny on me."

"Oh, Rose. I could've told you that, love. He's just the same as your dad."

"Dad married you, though."

"Yeah. Took a bit of persuading, let me tell you."

"Anyway." She broke away. "You don't understand. He's the last of the Time Lords, he's all alone. It's made him scared of getting close to anyone."

"Oh, I'm sure. They all have a sob story, that sort."

"Mum!"

"I'm sorry, I'm just telling you the truth. You think I don't know anything because I haven't been gallivanting around the galaxy in a time machine, but when it comes right down to it, men don't change – whatever planet they're from. What Mickey used to say about him was true."

"What did Mickey say?"

"That he was no different. He told me all about that other girl you met, the one he dumped years ago without so much as a thank you."

"He's nine hundred years old, Mum. So he has a few exes – what do you expect?"

"And you really think that you'll be the One? He's nine hundred years old, you're twenty."

"He said I could spend the rest of my life with him."

"Well, that was big of him."

Rose turned away.

"You came and told me first," said her mother, in a gentler voice. "That should tell you something, for a start."

"He's had kids before," she said, after a pause.

"Oh! Has he, now. And where are they?"

"They're probably dead! All his people were killed in the Time War. He only mentioned it in passing. I didn't like to ask him more."

Jackie gave her a look full of meaning. "Well," she said, "first things first. I'll make you an appointment in the morning, at the clinic, and we can get you properly checked out."

"No! Mum, I can't go to a doctor, not here! What if they do a scan and it's got two hearts?"

"Then that's something we're need to know."

"But they'll think there's something wrong with it. I can't go to a clinic here. There's no way."

"Don't be silly, Rose. You need to be seen to."

"I'll get the Doctor to take me somewhere out there, somewhere where they have alien babies all the time." A feeling of unreality and slight hysteria came over her as she formed that thought.

"No. If you think you are setting foot back in that machine and going anywhere, then you're out of your mind."

"Mum!"

"That's it, Rose. It's too dangerous. You've got a baby to think about now, you can't go back out there."

"I have to! The Doctor's not going to stop travelling and get a flat on the Powell Estate, is he?"

"If he had a shred of decency, he'd do the responsible thing. But no, I don't think he will."

"I won't leave him, Mum."

"It's not all about you any more!"

They both froze as the door to the flat clicked open and the Doctor breezed in with a bag and an aroma of roasting fat and vinegar. "Fish and chips all round. Best in the galaxy, accept no substitutes. Are we setting the table, or eating in the traditional manner with laps and fingers?"

The Doctor often seemed oblivious to atmospheres. He kicked his shoes off and made himself at home in the corner of the sofa, attacking the chips with his bare hands while Jackie slumped in her own armchair in dark glowering silence and Rose perched by the Doctor's feet, picking at her food. The smell was making her feel ill.

"Eat up," said Jackie.

"I'm not that hungry."

"Give 'em to me then. I'm starving." The Doctor snatched them from her hand.

"She needs her food," said Jackie, in a voice so laden with meaning that Rose was propelled to her feet.

"Come on, let's go for a walk," she said to the Doctor. She was terrified that her mother was going to blurt it out. If there was going to be a scene, she wanted to have some chance of controlling it.

It wasn't exactly weather for a walk, around a setting that was hardly picturesque. Darkness had closed in already, imperfectly illuminated by the few mostly broken wall lights along the alley between Churchill House and Lloyd George Towers. Upturned wheelie bins, strewn rubbish bags, discarded lager cans and smashed beer bottles, dried pools of vomit, worse things. Every time she came back, Rose noticed the details a little more. Every time, home seemed greyer.

She had the feeling that the Doctor didn't see these surroundings as squalid and depressing, or not in the same way. They had no power over him. It was all one to him, alien and exotic. It wasn't grime, it was local colour.

Three hooded youths were squatting in a stairwell as they passed onto the open concourse under the tower block.

"Lloyd George Towers," said Rose. "Rough end of town."

"I knew him!"

"You never."

"I might've!"

"You're so gay."

The hoodies hissed and jeered obscenities as they walked past. Rose thought she knew one of them, and they almost certainly recognised her. It was either her local notoriety, or the Doctor's appearance – which of course, round here, provoked ridicule in itself – which was setting them off.

"Ignore them," she muttered.

The Doctor took her hand, and turned to face them full on.

The hoodies were abruptly silenced, as if the Doctor had directed some kind of dickhead-stunning beam on them. Their faces were mostly in the shadow of their hoods, but Rose watched them cower back into the stairwell. No catcalls followed them as the Doctor and Rose moved on.

"You didn't even need to say anything," said Rose, in wonder.

"It's my evil eye." He winked it.

She waited until they were well clear of the gang, and alone under the fitful lights of the tower block. It was like standing at the edge of a very long drop and knowing she had to jump – terror so sharp it felt like she had swallowed it. "You know you said you were a dad once?" She glanced at him quickly when he said nothing, and his face was shadowed, wary. He was obviously thinking that she was going to press him to talk about that, and it was just as apparent that he didn't want to. "Well – it looks as if you're going to be one again."

She gripped his hand tighter by instinct, but she felt it loosen and fall away as he stopped and looked down at her. "Are you sure?"

Although she'd hyped herself up to expect a bad reaction, really she had been hoping and telling herself that he would leap about with glee or something. His stillness, the darkness of his eyes, the quietness of his voice, were what she suddenly knew she'd known would happen. "Yeah. I did the test. That was the real reason I wanted to come home."

He tipped his chin back and strode on, hands thrust in pockets, a little faster.

She hurried after him.

He ran his hand over his face and through his hair, then whirled round. "I mean, haven't you been doing anything? To stop it?"

"I didn't think it could happen! You and me – you're an alien – I thought it'd be impossible!"

He sighed angrily. "Of course it's possible."

"What. You knew that?"

"Yes! Er – yeah." He took a step back and looked aside, suddenly shamefaced.

"Why didn't you tell me?"

"I forgot! It'd been a long time!"

"Why, how many other humans have you knocked up?"

"None! That I know of… scary thought… Look, I told you. I don't exactly make a habit of it."

"What about Sarah Jane?"

"That was years ago – decades. That was before you were born!"

"Well, what about Madame de sodding Pompadour? That wasn't years ago, that was like six months."

"Rose, there was a very particular set of circumstances surrounding that situation, imperatives that I doubt you'd understand, complications – "

"Did you shag her?"

He started to reply, and then his face darkened again. "What have you been doing, Rose? Six months ago, and you never mentioned it once. Have you been saving this up, waiting for the worst possible moment to fling it in my face?"

"Fuck you!" She burst into tears.

He held her very close, tangling his fingers into her hair, pressing his cheek against her forehead. Even through the combined thickness of her puffed jacket and his coat, she could feel the odd familiar double beat of his hearts.

"I'm sorry," she sobbed, several times.

He hushed her.

What was this all about, another part of her mind thought. Why was she apologising to him, when he was the one who had been unfaithful – if fidelity meant anything to him, anyway – and then got her pregnant and seemed pissed off about it.

"That's what we were talking about, I thought," he said.

She gulped between a giggle and a sob. When she lifted her head from his neck he watched her face intensely, with his eyes serious and, perhaps, tender. It was the expression she found unreadable.

"Your mother is not going to want me back up there. She'll kill me or something."

Rose shook her head.

"Daleks, no problem. Cybermen, hmm – your mother on the warpath, no no no. I think I'll keep my head down for tonight."

"I'd better get back."

"Want to do a runner?"

They were just across the square from where the TARDIS was tucked into its usual corner. It was very tempting. His hands were pressing hers, and her whole body was flooded with warmth and relief that he hadn't decided to dump here there and then.

"No, Mum'd worry. I'd better go to her. I'll see you in the morning, yeah?"

She watched him from the top of the second flight of stairs as he let himself into the TARDIS, and waved.

Without warning, black crashing terror slammed into her like a freezing wave. What if the TARDIS engines started, and the blue box began to flash and fade? She was simultaneously gripped by an urge to tear back down the stairs and claw at the door, and a total inability to move at all. The panic attack ebbed away as the seconds passed and the TARDIS stayed silent and solid. If left her chest pounding and her legs shaking. She wobbled up the last steps to her mother's level and only just made it through the door and into the bathroom before she threw up.

"Rose! Are you OK, love?"

She flushed the toilet and pushed past Jackie, who was nosing round the half-opened door. "Yeah. Just leave me alone for tonight, Mum, OK?"

Safely in her bedroom, she stuck a pillow over her face and used it to muffle her tears.

"Rose."

His voice, in her blood, filling her. Too far away. Forever, far away. Utter longing, utter hopelessness.

She sucked air in a rush and shot upright.

"Rose!"

It was her mother's voice, and a gentle tap-tap on the door.

Rose sat still in bed as the intensity of the dream-feelings washed away, still tingling with the after-shock and the relief that whatever it had been about, it hadn't been real. The problem she actually had seemed almost comforting, in contrast.

Her mother had brought her tea, in her ancient Carebear mug.

Rose shifted upwards in bed and cupped it in her lap.

"Feeling any better, love?"

"Yeah. OK at the moment."

"I'm sorry about some of the things I said last night. It was the shock."

"Yeah. I know."

"Now, I've made you an appointment at the health centre for two this afternoon – and before you start, they don't have to do any tests, they can just make sure you're healthy. Do it for me."

"OK."

Jackie hovered for a moment, as if waiting for her to say something else, then left her in peace.

Rose sat back against the pillow, sipped her tea and thought about her conversation with the Doctor last night. Surprisingly, she had fallen asleep easily enough after a brief angry storm of tears. She supposed she had, after all, been reassured. She was glad she hadn't yielded to the strong impulse to go with his suggestion that they take off there and then, but she was incredibly heartened that he had made it. If he still wanted her to go with him, then he hadn't rejected her because of the baby.

The baby itself, well – she knew how the Doctor's mind worked. He was intensely focussed on the present. Funny that, for someone who called himself a Time Lord, but she guessed her rarely thought nine minutes into the future, let alone nine months. The prospect of being the father to a child six months or whenever down the line from now was probably not something he could make real to himself. Intuitively, she understood this.

That was why she had felt guilty last night over the Madame de Pompadour business. Of course she had known, at the time, that he'd slept with her. She'd known as soon as she and Reinette had faced each other. There was always that connection of understanding between women who'd had the same man – she'd had a strangely similar encounter with Tracey Cruikshank in the newsagents on the parade once, the day after Kevin Stone had gone off with her at Haley Dunwell's party. She hadn't liked it – the Doctor and his French tart, that was – but she'd swallowed down her hurt because it wasn't as if he was ever going to see her again, and she knew he was cut up about the way they parted, and she was too much in love with him to risk rocking the boat when he had come back to her anyway. In fact he'd come to her the same night, sad and tense, and she hadn't exactly kicked him out of bed.

He was right. If she was going to have made a fuss, she should have done it at the time. He must have assumed that she'd understood and forgiven him, because she'd let him make love to her that night and said nothing about it.

It surprised her how protective she felt, how responsible for him. He sometimes talked about how he'd promised her mother to look after her, but despite the eight hundred and eighty year age difference, she often felt that she was the one taking care of him. He was so vulnerable – sometimes like a kid himself – and he needed her.

She had to go to him and make things all right again.

She put down the half-empty cup on the bedside table, and lifted the curtain. From her bedroom window, she could just see the edge of the TARDIS across the concourse three storeys below.

Except, she couldn't. There were two boys playing wheelies on mountain bikes, and a black bin liner scudding across the concrete – but no blue box anywhere.