Warning: None, actually - there are no spoilers for Season 4 anywhere in this story. It's canon all the way up to the end of Season 3 of New Who ("Last of the Time Lords"). You may read without fear.

Disclaimer: Not mine. It's very sad, I agree. If it looks familiar, it's because it's also on LJ and Teaspoon.
Chapter Summary: There is an odd blue box humming, and it's up to Rose Tyler to investigate. There is an odd blue box humming, and the Doctor thinks he knows what to do with it.

Chapter 1: Humming

It should have been impossible, but impossible for Earth and impossible for Gallifrey were two entirely different concepts. Impossible for Earth to time-travel; impossible for Gallifrey to not.

So impossible was really just a matter of where you happened to be in the world. At this moment, he was in the one place where retrieving Rose was suddenly not impossible. In a single moment, a single place, a single fraction of a heartbeat, he'd have Rose standing nearby, touchable, unforgettable, and without a doubt, very, very, very angry, with him, specifically.

He didn't know if it would work. He didn't know if she'd even survive it. He'd never heard of anyone having done what he was about to do. He'd only seen the device sitting in front of him twice before in his entire life; he barely knew what it was. It could very easily result in two worlds collapsing into specks of dust.

He decided he didn't care, and did it anyway.

It should have been a good day, but good days for Rose and good days for Mickey were two entirely different concepts. Mickey's good days involved little or no reference to the life he'd left behind in their original dimension; Rose's best days were filled with them.

The day had started out well for Rose: she'd woken up, just herself and her mum in the house. Pete and the twins had gone off on some over-night school trip, something of a rarity. It wasn't that she didn't like Pete – she did, really – but when he was around, he usually served as a reminder that life was different. The same for the twins – as much as Rose loved them, as much as she knew they loved her, it was odd, having siblings, hearing her parents answer to other voices calling Mum and Dad.

But today was a good day: today Rose saw Jackie only briefly before racing out the door, the two of them shouting reminders at each other, and Rose hopped onto the nearest bus and within minutes was being whisked away to the center of the city, where the central Henrik's still sat, impervious, on its corner across from the Oxford Street John Lewis. Rose didn't go in but let her eyes feast upon it as the bus turned to speed towards Picadilly's bright lights.

A good day; the person clinging to the railing was listening to their iPod too loudly. Rose could just make out the Beatles' "Across the Universe". Someone nearby was unpeeling a banana. And two rows in front sat a ginger-haired man with a black leather jacket.

Rose closed her eyes, inhaled, and let a smile tug at her lips. Two years ago, this might have made her run screaming from the bus, the assault of memories too much for her to bear. Now the reminders around her were overwhelming just by the fact they existed, and for some odd reason, they gave her hope.

Hope for what, she wasn't certain. But it was with a heavy heart that she disembarked when the bus reached the Thames, and she began the final part of her walk towards Canary Wharf and Torchwood Tower. She would rather have stayed on the bus, in hopes that a man wearing pinstripes would board and complete the picture.

Instead, she saw a man wearing pinstripes as she entered the offices, but it didn't give her any sort of hopeful joy. The pinstriped man was Mickey Smith, hunched over a desk and scowling. Mickey always scowled when he wore the pinstripes, which was just as well, because he didn't look that good in them. Rose tried to close the door softly, but it slipped from her fingers and slammed. Mickey refocused his scowl onto her.

"You're late," he snapped.

"Bus," she said. "Run out of laundry again?"

"Huh?"

"Pinstripes," she said, surprised how calm her voice sounded. "You only wear them when there's nothing else."

"You can comment on my choice of clothing, or you can get on with it," said Mickey, his scowl not improving. "It's started to hum again."

Rose frowned. "Again?"

"Don't forget to wear the safety suit. Here's the results from last night's scans – and shut the door on the way out, would you?"

Rose took the envelope with the test results and pulled them out to scan them. "This doesn't make sense."

"I know," he said irritably.

"It's been sitting there for five years, and it starts humming for no apparent reason four years ago, then stops, starts up a week ago and then stops – and now it's humming again?"

"Broken record, you are."

"You looked at these, right?"

"Sodding things gave me a paper cut. That's my blood on the edge there."

Rose bit her lip. "Only…humming?"

Mickey looked up, the exasperation on his face waning just a little. "Yes, humming. Why?"

"Just…I don't know. A blue box humming in the basement on top of a few other things today…."

Mickey frowned, instantly getting it. "Pinstripes."

"Yeah."

"Impossible, Rose."

"I know. But…humming."

"Look, I'll send someone else to do it—"

Rose snorted. "Fat lot of good that would do – you and I are the only ones who can see it properly. Everyone else who looks at it just sees a odd fog of air hanging about. It's either you or me, Mickey, there's no one else who can do it."

"You get like this every time," said Mickey, most of the exasperation replaced with something more akin to concern. "You hear a song or you see a picture and you get this weird faraway vibe, Rose. It's impossible, Rose. You've got to let it go."

"Easy for you to say – you didn't leave anything behind when you decided to stay here," countered Rose.

"And neither did you."

"I didn't get to decide."

"You always said the Doctor wanted what was best for you, and he wanted you here. That's why he sent you in the first place, before you decided to take matters into your own hands and go back, and it nearly got you killed, the way Pete tells it. If Pete hadn't taken a chance to go back for you – you would have died, Rose. Can't you trust the Doctor that this is what's best?"

Despite all the reminders, Rose hadn't even allowed herself to think his name all morning, and hearing it from Mickey gave her something of a jolt. Worse, she knew that Mickey saw her reaction, because the self-righteous smirk he'd learned in the five years since Bad Wolf Bay spread across his face. Not only did Mickey think he was right, he knew she knew it, too.

"Yeah," said Rose slowly, hating that smirk. "Mickey? Thanks."

He didn't answer, and Rose couldn't help but think he should have. She shut Mickey's door when she left the office and walked down the hall. She stared straight ahead of her as the lift descended into the catacombs beneath the tower, determined to keep Mickey's words at bay, and almost breathed a sigh of relief when the lift came to a stop. She exited onto a long, sterile hallway, at the end of which was a single bolted door, marked only with a small nameplate reading "Room Negative 27". The keys were in her pocket, and she fished them out.

"Here we go," she said to no one in particular, and opened the door. The room was empty save for a small blue box no more than half a meter high sitting in the center of the room. It was perfectly square with rounded edges and resembled a bright blue gelatin mold. A distinctive, low-pitched, steady and altogether too-familiar hum filled the room, and only grew louder as Rose walked up to the box and crouched next to it. She'd seen the box often enough, when it was both quiet and when it hummed, but she'd never really felt such an urge to be so close to it as she did now. It ought to have made her uneasy, she knew – but it didn't.

Rose pulled the test results out again and studied them. The results were on a single page, marred only by the drops of Mickey's blood in the corner. They were the oddest results she'd seen in her life, contradictory at every turn and completely useless. Composition: unknown, organic. Age: unknown, circa five trillion years. Origin, density, mass, weight: unknown, unknown, unknown.

"A great big unknown, is what you are," she said softly. "All shoved in a little blue box. And today, of all days, you decide to hum."

She frowned, looking at the box, and without thinking, reached out to touch it. It was only as her fingers reached the surface that she realized she'd entirely forgotten about Mickey's warning to put on the safety suit, which would have covered her hands. But it was too late – her skin made contact, and for a moment, she could feel the hard, smooth, strangely warm surface, and just as she'd begun to pull away, the box gave way and her hand slipped neatly inside, as if she'd pushed into a blue custard.

Surprising, a little alarming, and rather sticky. But the reason she began to scream was because something inside the box took hold of her hand – and pulled. Without warning, Rose's good day became impossibly familiar, and her entire world went blue.

"Rose…Rose, I know you're awake now. Rose, open your eyes."

"Blue," muttered Rose. It was the only thing she remembered, the color and smell and taste of it. Her mouth was filled with blue cotton candy, she'd been swathed in blue fabric, her nose was filled with sickeningly sweet-and-sour blue perfume. Her head pounded, her muscles ached, and her chest felt as if something wasn't quite right. Her fingers felt vaguely sticky, as if they'd been coated in gel and hastily washed with a damp towel. She was lying on a cushion of some sort, with a light blanket over her – both of which she had no doubt were blue – and she could feel someone hovering over her. He laughed, a little, just a little, and she felt a hand in hers.

"That's right! Open your eyes, Rose, that's my girl. It's not so hard! For me, Rose, come on, now."

He was right, but it hurt anyway, eyelashes glued together by the blue goo she'd been pulled through, by a hand that felt too familiar…a hand that held her own, tightening around it every time she moved. She opened her eyes, and when she saw the man standing there next to the cushion, screamed. Again.

"Rose! No, no, stop, it's okay!" He reached for her shoulders but she was quicker and moved away, only to find herself falling off the cushion – which was really a very thick blanket on the floor.

"YOU…THAT…BLUE...YOU…impossible!" she shrieked. Her heart was pounding so hard it hurt; she felt light-headed and ill. There were remnants of blue hanging to her skin and clothes, like custard. And yet, there he crouched, familiar and vulnerable, and Rose wondered if she'd stumbled into a nightmare.

He knelt next to the blankets, looking so much like himself, hair mussed, brown pinstripe suit slightly rumpled, tie askew – and white trainers without a doubt tucked underneath – that the grin on his face didn't seem the least bit incongruous, especially considering her frantic fury.

"Oi," he said cheerily. "Who said impossible?"

"YOU DID, YOU GREAT BLOODY STUPID TIME LORD!"

"Did I?" He frowned, thought, and then grinned again. "Yeah, been wrong before. Probably will be wrong again. Pretty sure I'm sitting here, though—" He pinched his arm and jumped. "Yep, hundred percent here. And you – your head's hurting you, I imagine, so you've got to be here too. That can't be impossible, can it, if we're both still sitting here?"

Rose stared at him. He was certainly talking enough. But…. "It's a dream. You're a dream. I've hit my head."

"If it were a dream, what would I do next?"

Rose blushed. Hard.

He blushed. Harder.

"Where am I?" asked Rose, trying to change the subject.

"Tardis console room. Grating," said the Doctor, knocking the grated floor helpfully.

"If this were a dream," said Rose slowly, "you would have pulled me somewhere a lot more comfortable."

"Yeah, well…."

"But that means – it's not a dream."

And with that, she launched herself across the blue blanket that separated them, and for the first time in five years, felt the Doctor's arms wrap around her, and his head rest next to hers.

Mickey Smith was not having a good day. The only clean trousers in his closet were pinstripes. The only fruit in the cafeteria had been bananas. There had been an ungodly number of people wearing leather jackets in the lift. As if this wasn't enough, the blue box in Room Negative 27 was still humming. If it had been doing that whoosh-whoosh sound he remembered, he might have destroyed the thing, protocols be damned, but worse, it had somehow sucked Rose Tyler into it, leaving no trace of her behind.

Literally, no trace, as in having never existed.

"Sir, I have no idea what you're talking about," the guard was saying to him. "There wasn't anyone down here this morning."

"I sent Rose Tyler myself, sergeant—"

"Who?"

"You of all people, sergeant, ought to remember, you only dated her for three months last year," snapped Mickey, and then sighed, rubbing his temples.

"I've never met anyone named Rose Tyler, sir," said the sergeant.

For some reason, the answer didn't surprise him. "Never mind. I've got a headache. That stupid humming—"

"Humming, sir?"

"Yes, humming, from the box, can't you hear it?"

"There's no humming from this room, sir," said the sergeant slowly. "And no box, neither, just a sort of a blue fog there in the center."

Mickey looked at the sergeant, and then looked back at the box. If a box could be said to hum happily, then that description certainly fit.

"Must be the headache," said Mickey irritably. "Where are the test results on this thing? The ones run last night?"

"Test results?"

"Yes, test results, we ran tests on it yesterday!"

The man shook his head. "Sir…no one's come in here for five years, except for you. I've never even been in here. If anyone ran tests on this contraption, it was five years ago when you first found it and moved it down here."

Mickey blinked. "And Rose Tyler, sergeant. I moved it with Rose Tyler."

The sergeant clearly did not believe him, but wasn't about to argue. "Sir."

"Right," said Mickey, somewhat dazed "Well, in that case, I have an errand to run. Hold down the fort, sergeant. Lock this door and don't let anyone in this room until I return."

"Yes, sir."

Mickey didn't bother to watch the door lock, although he reflected that he ought to have done. In truth, he didn't much care. He was certain – positive – that there was something very wrong going on. No matter what the sergeant said, Rose had been with him when he had found the box, in the aftermath of Canary Wharf. He remembered it clear as day, along with the intervening years, just as he remembered ordering testing on the blue box the day before, and handing those results to Rose that morning. He remembered the way Rose had acted so strangely before she'd gone, and the way his headache had come on so fast at the same time that the lights had flickered twenty minutes before.

He could have sworn the day had been bright and clear that morning, and now low clouds hung over London, the sign of a storm front moving in.

All of a sudden, Mickey had a powerful urge to call Jackie Tyler. Just to see. Just to check. Just to make sure that Jackie Tyler existed at all.

"Explain it again."

"I've explained three times—"

"I know, but explain it again, this time in English."

"I am explaining in English."

Rose waited, and after an extended sigh, he started. "Every time you make a decision where there is the possibility of a substantially different outcome, it results in a parallel world. For every decision made, there's a focal point – like a crossroads, a place where two roads diverge."

"Like the poem," said Rose.

"Yes! Like the poem. You on one road, me on the other. The blue box is a crossroads. It reflects the two possibilities – a world with you, and a world without you."

"But – did you reverse the decision?"

"No, no one can do that. I don't think it was my decision that caused the crossroads. I've had time to think about it, Rose, I think it was Pete. When he decided to come back for you, and took you to the other world – well, he was saving your life. You would have died in the Void if he hadn't done it, so he saved you. A world with you. A world without you."

"But you said there's thousands of parallel worlds – why isn't the world overrun with these boxes?"

"It probably is, but I've only seen them three times in my life."

Rose rubbed her temples. "It makes my head hurt. That was you, pulling me through?"

"Yep," he said, a hint of pride.

She thought for a moment. "A bit like…oh, I can't put my finger on it. It coated me all over, didn't it, that custard? I feel like there's something of a film on my skin, sticky almost."

"I washed off as much as I could, you were dripping with it. I don't think I did a very good job, but I was more worried about the—" He cut himself off quickly. "No matter, you can go take a shower if you want, plenty of hot water, wash yourself off better than I could do with a damp towel in here."

"But how did you know it was me?"

He laughed. "Think I don't recognize that hand? I'd know it anywhere."

"A portal between there and here—" Rose's eyes brightened. "I'm here."

"You're here," he said happily.

"I'm really here?"

"Really here," he confirmed, the happiness overflowing. "My Rose!" And he took her hand, squeezing it.

"Doctor! You did it! Oh, this is brilliant!"

"Brilliant," he agreed.

"My clever Doctor!"

"Clever me!"

"A portal between there and here – I can't wait to tell Mum—"

There was a pause, a brief tiny one, so short Rose didn't even notice. "Ah – Jackie?"

"Do you know, there's no Selfridges in that world? Finally Mum has money to burn and nowhere to spend it! And Liberty's is just a shoe shop! Mum would love to pop back and forth and do a little shopping."

"Plenty of time for details later," he said, jumping up to his feet. "You must be wanting a shower…."

"What's the point, if I'm going through blue custard again to tell Mum the good news?" laughed Rose.

"Ah, Rose, we've got all the time in the world – what would you like to do first?"

"I like now," she said, and then looked around the control room. "Wait. If the box is a reflection, then it's here too. Where is it?"

"Couldn't go bringing it into the Tardis, could I? Strange blue humming thing like that, might have blown us both to kingdom come and where would we be?"

"But – I wanted to see it."

The Doctor paused. "Maybe a shower first…."

Rose stood up. "What are you hiding? Why can't I go to the blue box?"

"Yes, a shower would put you back to sorts, wash the rest of that custard as you call it off, hot steam push that headache away—"

"Doctor!" Rose felt like screaming again. "Why won't you answer the question?"

The Doctor looked at her, straight into her eyes, and that hard bit came in again, the way it always did when he told her something she didn't particularly want but needed to hear. "I can take you back to where I found the crossroads, Rose, but I can't guarantee it will still be there. I found it in Canary Wharf, in the ruins of Torchwood Tower, and a minute after you appeared, coated in blue and slipping into a coma, the tower began to collapse. That was four days ago. I'm sorry, Rose, but the crossroads is gone."