The Ninth Doctor had insisted that Clara return to her apartment while he tinkered with the TARDIS to see if there was any way he could wire it to travel back to the exact moment it had collided with his own TARDIS. Clara proved rather difficult, however, and insisted she stayed with the Doctor.

"You know I've met you all," Clara commented, trying to make conversation as this particular incarnation of the Doctor wasn't exactly a conversationalist.

The Doctor remained quiet as he continued to tinker away. After a bit he said, "Impossible."

"It's the truth," Clara said defensively. "I met the lot of you, all at once."

The Doctor was lying on his back underneath the exterior of the TARDIS, disconnecting and reconnecting different wires. "The only way you could have done that would be to visit my tomb. And I can only imagine the extremities one would have to go through to get to it."

Clara remained quiet, not wanting to reveal too much to this past incarnation of the Doctor. She sensed that he was the type who didn't want to know too much either. Suddenly a siren began to go off, bathing the TARDIS in crimson red.

The Doctor quickly got out from underneath the console and stood up looking for the source of the siren. "What is that?"

"That's the signal that goes off whenever there is an imminent threat to the immediate area," Clara said, eyeing the Doctor suspiciously. "Don't you have that in your TARDIS?"

"More or less," the Doctor replied. "It's not as refined a system as this, but it works."

Clara tapped one of the screens and an image appeared. The Doctor appeared by her side and looked on. "Doctor, what exactly is that?"

He shook his head back and forth; unsure of what exactly it was that he was looking at. "There's probably no sense in telling you to stay put, is there?"

"None whatsoever," Clara replied.

"It looks like this is happening in the heart of London, we best get going," the Doctor said. Clara nodded in agreement and the Doctor pressed a button that would take them exactly to the location that the screen was showing.

Meanwhile the Twelfth Doctor was attempting his best impersonation of his former self. "I'm sorry Rose, but I've so much to do."

Rose, who remained on the other side of the TARDIS, was not going to let up that easily. "I'm going to wait here until you come out, or else I'll send my mum after you."

The Twelfth Doctor reached back in his memories and found an older blonde woman whom he found rather irksome. Not wanting to deal with her he decided he had no other choice than to let Rose inside the TARDIS. He stepped back to a corner of the TARDIS so that he was immersed in the shadows so Rose wouldn't see his face, at least not right away.

The doors slowly opened and Rose entered. The Doctor could see she was wearing a simple pink t-shirt and blue jeans. Immediately he was flooded with memories of all their adventures together, it was almost too much for him. But he had to pull himself together.

Rose sensed that there was something off about the Doctor, though she wasn't quite sure what it was. "Doctor, is everything alright?" she asked. As she moved closer to the Doctor he inched closer and closer to the wall. At this point she knew something was wrong.

"Please, Rose. Don't come any nearer," the Doctor said.

This stopped Rose. She knew the Doctor's voice, and this voice; it was the voice of a stranger. "Who are you?" she asked, her voice rather shaky.

"I'm afraid at this point in your life you would not believe me," he replied.

Every part of Rose wanted her to turn around and leave, but there was something keeping her where she was. "I won't repeat myself," she said.

"Nor will I," replied the Doctor. He then stepped out from the shadows and Rose saw the Twelfth Doctor, a man she did not recognize whatsoever. "I am the Doctor, though not the one you're familiar with."

Rose stumbled backwards and began to fall backwards, but not before the Doctor rushed to her side and helped her up. She looked into his eyes and saw no threat, perhaps a little crudeness but that was it. Rose shook her head back and forth. "No, you're not him. You can't be." Suddenly the TARDIS jolted forwards. The engines started up and it began to take off. The Doctor had to grip the railing for support, Rose doing the same. "What is happening?" Rose asked as the TARDIS flew through space faster and faster.

"Hard to say," the Doctor replied. "If I'm not mistaken it would appear the TARDIS is being summoned, and from a great distance too."

"Summoned? By who?" Rose asked.

The Doctor extended his hand and pulled a lever but it did nothing. "I can't disconnect us from whoever is summoning the TARDIS. This can't be good."

"And I'm on board a spaceship with something claiming to be the Doctor that clearly isn't," Rose said. Just as the TARDIS came to a halt the Doctor turned to Rose.

"I'm rather forgetful when it comes to my past companions. How much do you know about regeneration?" asked the Doctor.