The Doctor found himself alone in his TARDIS, normally a dangerous concept but something that at this point was a necessity. His companion, Rose Tyler, needed time to collect herself. The Doctor had shown up one day and whisked her away to a life full of aliens and adventure. It was amazing but Rose owed it to her mother to spend some time with her. And especially since the Doctor had accidentally brought Rose back home a year later than when she had left, he knew it was time to step back for a bit.

He had taken to working on a few short circuits the TARDIS was experiencing. The Doctor was attempting to disconnect a loose wire. He had his sonic screwdriver sideways in his mouth in case he needed to use it to make any adjustments. Suddenly he was jerked backwards by the full force of the TARDIS. He fell backwards onto the floor, hitting his head in the process. The Doctor attempted to regain his balance but the TARDIS was rocking back and forth, which made no sense to the Doctor as the TARDIS was stationary.

The force was enough to keep the Doctor unbalanced, but not enough that he couldn't do his best to stop the TARDIS from exploding. He twisted knobs and pulled levers but nothing seemed to be working, only increasing the frustration of the Doctor. Suddenly he was blasted backwards once more and landed on his back.

After the Doctor was blasted backwards the TARDIS came to a grinding halt. The lights in the TARDIS continued to flash until a hand pulled a lever on the console and set the lights to their primary functionality.

"Well that was just a lot of nonsense," a voice said from nearby the main hub of the TARDIS. The Doctor stood up immediately, despite the immense amount of pain in the back of his head, to see just who was in his TARDIS and why the advanced security system hadn't thrown the unwanted squatter out.

The Doctor immediately noticed that the TARDIS he was in was not one he recognized. There were shelves upon shelves of books surrounding the walls and it appeared to be more of a high-tech look compared to the steam-punk look he was accustomed to. A woman's voice then caught the Doctor's attention. "It wasn't nonsense, Doctor," the woman said. "Something crashy happened and I think we should look outside."

The Doctor then saw an older man dressed in a Crombie-style jacket with red lining and a white collared shirt. A woman wearing a simple brown mini-skirt and a red sweatshirt stood at his side. Neither person looked familiar to the Doctor but he was beginning to have his suspicions as to what happened when the TARDIS began to go haywire.

The Doctor cleared his throat and the woman and older gentlemen took their gaze away from the screens they were looking at and instead looked to the Doctor. The older gentlemen looked to the Doctor with a look of befuddlement while the young woman instead looked to the Doctor with shock.

The older man cleared his throat as well and said, "May we help you?" in a thick, Scottish accent.

The younger woman, Clara Oswald, whispered to the older man, "Doctor, don't you realize who that is?" Revealing the Ninth Doctor's suspicions, he realized exactly what had happened.

The Twelfth Doctor looked to Clara, and then to his former self, and back again. "Don't be absurd, Clara. That can't possibly be me. I think I'd remember meeting myself."

"If I might," the Ninth Doctor interrupted, "can I ask just exactly what you are doing?"

The Twelfth Doctor straightened the sleeves of his jacket and leaned against the console. "Not that this is any of your concern old fellow, but I was returning my dear friend here home. It seems, however, that I made a most unfortunate error."

The Ninth Doctor raised an eyebrow unsure of what to think of this other version of himself. "And what might that error be?"

"I intersected one of your time streams and it appears that both of our TARDIS' have combined," explained twelve.

"A physical impossibility," nine replied, "a TARDIS inside another TARDIS, don't be daft. We'd rip a whole new black hole into the solar system!"

"They're not inside one another, they've merged together," explained twelve. He then snapped his fingers and the all too familiar layout of the Ninth Doctor's TARDIS appeared. "See?"

Clara looked around with mild interest. "Not too shabby."

"Oh please," twelve replied, "far too dusty." He snapped his fingers once more and the design of his own TARDIS reappeared.

Clara looked to the ninth doctor who looked very unamused. "What are we going to do about him?"

"I may have been knocked backwards, but I can still hear," nine said.

"With those ears what couldn't you hear," twelve replied. Just as nine was about to retort his future self turned back around and began messing with all sort of levers and pullies.

"You know I can be of assistance," he said.

The Twelfth Doctor sighed and looked to his former self, "I'm well aware of what you can do. But it would be best if you stayed back and interacted with me as little as possible. You know better than anyone what happens if you interfere."

"HA!" Clara exclaimed. "You're one to talk, Doctor."

"Hush now," twelve said. "I think I've figured this out." There was a dial he was turning, almost like a combination to a safe. Just as he turned it to the left one last time he pulled a long knob up and let it drop. Suddenly the two TARDIS' began to diverge from one another. It appeared that the Twelfth Doctor had been successful.

He found that the TARDIS was working properly again and that he was on course, though he wasn't quite sure where that was. Ready to boast in his success, the Doctor turned to his side but found Clara was not there. His former self was also absent, but that was what he had wanted. Looking at the readout and the design of his TARDIS, he realized just exactly what he had done.

Meanwhile the Ninth Doctor was with Clara in the Twelfth Doctor's TARDIS whizzing through time and space. "What happened?!" Clara exclaimed after the TARDIS had taken off without her Doctor.

"It would appear that my future self managed to pull the two TARDIS' apart but did so incorrectly. You and I are in his TARDIS traveling to your home, while he is in my TARDIS traveling who knows where," the Ninth Doctor explained.

Clara shook her head back and forth. "This isn't right. Take us back!"

The Ninth Doctor took a calming breath before saying, "To do that would be impossible. What my future self did was something that could only happen with one in a trillion odds. To do so again would take probably all of the lives I have left." The TARDIS then came to a stop. "No, we'll have to figure out another way."

The Twelfth Doctor wasn't having any better luck. The TARDIS he was in had also found a landing point. The readout on one of the screens had read London, England. The year was 2005. Having an immediate sense of foreboding the Doctor was hesitant to leave but a knock at the door of the TARDIS stopped him dead. What came next did so even moreso.

"Doctor, is that you? It's me, Rose," came the voice of Rose Tyler, his former companion.