A/N - I always enjoyed the Doctor Who Unbound range, and I often ask myself 'what ifs?' when I watch Doctor Who. Anyway, I don't own Doctor Who or the concept of Sliders or the characters.

Please let me know what you think.

Parallel Worlds.

Dalek Invasion of Earth.

Mickey's gone, he's actually gone! Rose was thinking to herself as she changed out of her maid uniform which she had used to gain access into the Tyler Mansion. She was pleased to get out of it; Rose had never liked wearing formal uniforms, although she had enjoyed wearing her schoolgirl uniform when she had been going through puberty. She just couldn't stand the thought of being like everybody else when she had her own personality to be proud of.

But right now Rose couldn't give any thought about being satisfied she was just back in her own clothes. Mickey was gone, he had wanted to stay behind in that parallel world to fight off the Cybermen that were still there.

Rose grimaced as she thought about the Cybermen; she had known vaguely about them after she'd seen that silver robot head with the handlebar things attached in Van Statten's museum. The Doctor had confirmed there were Cybermen in their own universe, and while at the time she'd observed that little detail to the Doctor, her experiences of the Cybermen was limited, what she had seen in their converted Battersea factory had horrified her…

When the TARDIS had suddenly exploded in the Time Vortex, and fell through a hole into that parallel world, the first thing Rose had seen had been that poster of her dad, Pete Tyler. The moment she had seen the poster, heard his voice as he'd said "Trust me on this!" Rose had been desperate to see him.

Where was the harm in that?

Rose simply could never understand why the Doctor, who had lost his own family and friends, hell even his planet, could not understand how she felt; surely if his world and the Time Lords had existed in that universe, wouldn't he want to visit them?

Rose snorted, annoyed with herself for not even considering asking her friend that question, and it was something she would have to bring up with him when she spoke to him next. She knew she would need to be careful, though; the Doctor was incredibly touchy about the Time Lords, and the subject of the Time War and that little trait had only seemed to have grown worse since the Doctor's regeneration. Where her last Doctor had been full of rage, this new Doctor was quieter like he was a volcano under pressure. Somehow that was even worse.

Rose had managed to persuade the Doctor to come with her to the Tyler mansion - getting the details hadn't been difficult since Cybus Industries had the means of patching into her phone, even if she hadn't seen any sign of a mobile phone, and why would she? Those people had used Ear Pods which downloaded messages into the brain - when she had learnt her dad was not only married to a parallel Jackie, but Rose had gotten the idea into her mind she could become their daughter.

They hadn't had her. All they had was some Yorkie named Rose, something which had made the Doctor laugh his head off. All Rose had wanted in her life was to have her father in her life, so they'd be one big happy family; sure she knew her parents hadn't had an ideal relationship, Rose hadn't been able to deny that when she'd saved her dad when she'd travelled with her old Doctor and messed time up as a result, but couldn't she do it in this reality?

Of course, the Doctor had condemned the plan and told her repeatedly Jackie and Pete were not her parents. But they were in her mind, and that was more than enough for Rose.

Unfortunately, her hopes had collapsed when the party had been ruined when the Cybermen had crashed the party and they had begun to kill the guests. Jackie had been separated and she'd been caught by the Cybermen, while Pete had come with her and the Doctor with the Preachers, their leader was Mickey's own parallel counterpart!

Pete had been the one to tell them what Lumic had been doing when he had created the Cybermen. The man was dying and he had been determined to find a way of keeping the brain alive, at any cost. When she had seen those people marching towards the Cybus factory in Battersea, Rose had wanted to help by taking off their Ear Pods but the Doctor had stopped her. Rose was glad he had otherwise she might have killed someone as needlessly as Lumic had.

Lumic might have wanted to save his own life, but while Rose could appreciate somebody's desire to live forever, she didn't understand why he had sought to impose it on the entire world…

Had Lumic decided he didn't want to live forever by himself? Was it really that simple?

Thinking about it, Rose considered what she had seen in that universe with the zeppelins and the Ear Pods and their slightly more advanced technology - the Doctor had said the world was more advanced and not that far off of her world, which was a scary thought since there was a chance the Cybermen could be recreated on her Earth! - and her own memories of the development of mobile phones.

Rose had grown up in the 90s and the early 2000s, and she had seen how rapidly technology had grown and developed; the idea of the Ear Pods appearing in her reality wasn't absurd at all.

Was that the reason Lumic had insanely decided to cut out people's human brains and stick them inside those Cyber suits, he was treating the Cybermen as the newest gimmick everyone just had to have? The thought was horrifying for Rose, especially since she and her dad - Pete - had gone into the factory to find Jackie, only to discover it was too late.

Rose was just left stunned following the battle with the Cybermen in the parallel world after the TARDIS had fallen through what the Doctor had called a crack in time, but what chilled her to the bone was the dismissive way Jackie in her Cyberman body had just coldly dismissed her human life like it was inconsequential.

Speaking to the Jackie-Cyberman was like speaking to a real-life robot; the thing wasn't speaking anything like Jackie at all, it was just Jackie's reprogrammed brain without the soul.

Rose had thought the Daleks were terrifying with their desire to exterminate everyone and everything that was not like them, and she had been horrified when the Dalek Emperor had kidnapped humans for 100 years and pulped them just to find one single cell in a billion to nurture into a Dalek creature for his growing army, but what the Cybermen had done to people's souls, just cutting out what it meant to be human…

Rose immediately pushed down any nausea she felt at that point, and she focused again on the true facts. She would never see Mickey again, but she couldn't accept that any more than she could have accepted the possibility of Pete walking away until he had just before they'd left in the TARDIS.

Why couldn't they see Mickey again? Okay, the Doctor had been horrified when the TARDIS just went completely dark, and he'd claimed the ship was dead. Rose knew the TARDIS was alive, but the Doctor had been able to save the ship. He'd used that glowing crystal thing, and it had held up against the Cybermen.

So surely the TARDIS could travel into other parallel universes, right?

How hard could it be for the Doctor to find another crack in time?

Once she was fully dressed, Rose went off towards the console room.

X

He had honestly thought he'd lost her, that was what was going through the Doctor's mind as he finished tying his tie around his neck. When Rose had left the console room and headed for the wardrobe, barely heeding his warnings the architectural reconfiguration system might be slightly out of whack as the TARDIS recovered from falling into that parallel universe and resulting in him checking it and fine-tuning it so then she didn't wind up lost in the bowels of the TARDIS. With what had happened, that was the last thing they needed right now.

As he walked up to the console and touched the coral surface of the current desktop, the Doctor winced at the sight of the burn marks on the surface. They'd just had a close call, he could see that. He had very nearly lost the TARDIS, and all because he and Rose had been playing some stupid prank on Mickey. The Doctor could see his mistakes now, and he was determined not to repeat them.

Once he was finished getting dressed in his own clothes - it had been relaxing in a way being in a tux, but it just wasn't him, the Doctor walked to the console and checked the readouts. The TARDIS had just breached the interdimensional barriers between the two realities, now all he needed to do was seal up the crack in time for good. As he got to work, the Doctor took a moment to reflect on the last adventure he'd had.

Travel into parallel universes was possible and easy when the Time Lords and Gallifrey had existed, but now it was much harder. The walls had been sealed off during the Time War, but if there was one crack leftover in the Vortex, then there were bound to be more. The Doctor knew he would need to prepare some kind of program to make sure they didn't fall into another, but there was time for that later. Right now he needed to set up the dimensional stabilisers.

The golden years where a severely damaged TARDIS could be taken back to Gallifrey for repairs were gone. Gallifrey was gone, leaving just himself behind to pick up the pieces, and if this mess hadn't convinced him of the need to be incredibly careful with his ship, then the Doctor didn't know what wouldn't.

He had visited parallel universes before; that mess in that fascistic Earth aside, the only times he had frequently visited a parallel world had taken place during his seventh and eighth incarnations. But now the Time War was over, well it had just become even harder.

"Doctor, I wanna go back for Mickey," Rose announced as she walked into the room.

The Doctor cursed Rose for her timing. "We can't," he gestured to the screen; it showed a 4-D image of the Time Vortex with a large multidimensional 'cut' in it which was being sealed. Rose took a look at it, and the Doctor could see the lack of understanding right there.

"What is that?"

"That is the hole we fell into. The TARDIS has finished sealing it up, and I am not opening it again," the Doctor finished with a glare sent towards her.

"Doctor-," Rose instantly began gearing up to argue, but he wasn't going to let her bite.

"No, Rose. Mickey made his choice to stay in the parallel world to fight the Cybermen. At the same time, I made it clear we would have to seal the crack up. It's too late now; Rose, if I reopen that crack, I would be putting other time travellers in danger, and I can't do that."

"We got out-!"

The Doctor wished he could one day sit Rose down and explain to her the dangers of playing games with time travel. He should have known Rose wouldn't have learnt from her mistakes when she had created that alternate timeline when she had saved Pete Tyler's life, only to discover things weren't as wonderful as she had thought they would be. She hadn't learnt anything from that, why would she learn from them now when she was willing to cause so much damage now?

"Yeah, but others might not be so lucky. And besides, how do we know we'd arrive in the right universe?"

"But the crack-!"

"It would likely open up into a different universe, and I am not going to do that, Rose. The TARDIS is still too badly damaged, right now all I want is to find a nice little time rift and soak up the energy-," the Doctor swung around to the console screen as an alarm sounded. "Oh no," he hissed in horror.

Rose, realising that he wasn't faking it, leaned over next to him. "What's wrong?"

"We're not in our universe, well we are, but we're currently mingling with other timelines that split off from the main timeline," the Doctor said quickly as he tried to make her realise how serious this was.

"Is that possible?" Rose looked at him in sudden fear. "You mean we're stuck again?"

"No, not quite. We're not in another parallel world, we're close enough for the TARDIS to repair herself, but we're just outside our timeline and are interacting with other alternate timelines that have split off from one another over the centuries," the Doctor raced through his knowledge of parallel timeline and reality theory to explain how this could have worked, and he wondered if the universe had 'pushed' away from the realities the Time Lords had sealed away with the Axis to preserve itself.

"Other alternate timelines? How many?" Rose demanded.

"That's the problem, I don't know for sure. But there are lots of them. We'll have to jump through them in order to find our way back."

"Pardon?"

"What?" The Doctor turned to Rose.

"You just said we needed to jump from these worlds to the next."

"Yes, I did, didn't I? The good news is the old girl has a good map of the universe in her records, so finding a way back won't be hard," the Doctor clarified as he began a basic temporal scan of the timelines ahead of the TARDIS. "The original universe is out there, with the others floating around as if they were bubbles; it's not how this all works, but just think of a bubble."

He stopped as he took in the results of the scan, staring at the results of it in horror.

"No," the Doctor whispered, stepping back from the console, staring at the screen with an expression that combined hope and dread in a way Rose had never once seen before. "It can't be…."

"What is it?" Rose asked.

"My planet. Gallifrey. It's….its in some of the universes ahead," the Doctor's expression was hollow.

"What, how? You mean it's there now?"

"Yes," the Doctor replied, looking at Rose with a brief heartbroken looking in his eyes before he turned back to the screen. "From what the scan just showed, there are over a dozen realities right ahead where Gallifrey exists."

"A dozen? Does that mean we're gonna meet other Time Lords?"

The Doctor's hopeful and heartbroken expression faded as he remembered something vital. "No, that's not a good idea."

Rose suddenly recalled her earlier thoughts. "Doctor, what's your problem with meeting Time Lords from other realities? Surely you'd be happy to meet them?"

"Rose, my relationship with the Time Lords in our home universe was always flexible; I have no idea what my counterparts are like in other realities," the Doctor said as he recalled a story Romana had told him about how she, Braxiatel and Narvin and Leela had travelled to other timelines and they'd encountered a reality where the Time Lords were interventionists who delighted in changing history while his counterpart was Lord Burner.

That was one world he would like to avoid; if the Time Lords of that reality tried to break into his timeline.…

The Doctor was broken out of his thoughts when the TARDIS started to materialise. "We're landing in one of the timelines now, Rose," he stated the obvious, but he was too distracted from his mishmash of thoughts to think of anything better to say.

Travel through alternate timelines was not easy, and if he had learnt anything from his eighth self had travelled into alternate timelines following that dark mess with the Faction and Gallifrey, the Doctor knew he'd need all the help he could get.