In a laboratory at the UNIT base, Doctor Elizabeth Shaw checked her part of an experiment involving the effects of something long-winded and practically unintelligible to the average person living in the late twentieth century. For someone who knew the Doctor, however, the experiment was a way to prove to him that the scientists at UNIT were – BANG!

Liz looked up to see black smoke pouring from inside the police box. She hurried to the door (it wouldn't do for the Brigadier to come in and see that she'd let the Doctor kill himself), and the Doctor leaned on her, coughing. He was muttering under his breath as she helped him to a chair. A dreadful noise sounded, a sort of mechanical wheezing, and the Doctor leapt to his feet, as much as he was able to leap.

"No," he cried rasply. Much to her surprise, a second police box appeared next to the Doctor's. A man stepped out of the second box, followed closely by a woman. The man was in the middle of explaining something, but he trailed off as he noticed his surroundings.

"Guessing this isn't Axos four then," the woman quipped. "Where are we? Wait, hold on, when are we?"

The man grinned. "I have absolutely no idea."

The Doctor straightened. "Hello," he said civilly. "What brings you here?"

The other man looked at the Doctor, then his eyes wandered to the TARDIS, and finally landed on Liz. "Oh. Hello. Sorry, didn't mean land here. Must have typed in a one instead of a zero in the space-time coordinates and the TARDIS brought us here."

"A most fine excuse for crossing one's timeline, Doctor," the Doctor said, striding over to where the other man stood.

"Crossing one's timeline?" The woman asked. "Hold on, Doctor, are you here somewhere else?" Doctor? Liz thought. That's completely impossible.

"Here somewhere else?" The Doctor said, affronted. "I assure you, my dear, that I am the Doctor. The definitive article, of course."

"Okay, fine, yes. Okay, Martha Jones, meet the Doctor. Doctor, Martha Jones," the man in pinstripes said. His eyes lit when spotted her across the room. "Liz! Liz Shaw!" He sprinted over and enveloped her in an embrace. Liz stiffened.

"Hello."

"Hello," the man said cockily.

"Do I know you?" Liz ducked out of the man's arms.

"I should think so," the man said, wounded. "I'm the Doctor." Liz looked from the stranger to the Doctor.

"He's you?" She asked, incredulous. She could hear the other woman asking the other man the same question.

"Apparently," the Doctor replied.

Liz looked back at the new Doctor. "From the future?"

"Certainly not the past." An idea came to the Doctor. "Yes, I wonder…" And with that, he cut off his successor, asking questions about the Time Lords and his personal future.

Liz turned to the woman. "We may be here a while. The Doctor tends to technobabble quite a lot. I shouldn't wonder if he talks your Doctor's ear off. Shall we get a coffee…?"

"Martha. Martha Jones. Coffee sounds amazing, you would not believe the day I've had. Then again, you know the Doctor so maybe you would." She laughed incredulously. "Something normal will feel really nice."

"This way. I don't believe that they'll even notice we've gone." Liz led the other woman into the corridor.

"Who're you?" Sergeant Benton was at the end of the corridor.

"She's with me," Liz said calmly.

"Doctor Shaw, all due respect, only the Brigadier can approve guests on the base." Benton unclipped his radio. "'Benton to the Brigadier. Unauthorized guests in the Doctor's lab. Repeat: unauthorized guests in the Doctor's lab.' Sorry, miss, but I'll have to ask you to stay here, at least until you've been authorized by the Brigadier."

"She's with the Doctor," Liz looked at Benton, who stood his ground. Luckily, the Brigadier wasn't too far away.

"Benton, report."

Liz jumped in before the sergeant could say a word. "She's with the Doctor. He's in his lab. We're getting coffee. If you want to know more, go speak with the Doctor. I daresay he knows more about the situation that we do."

The Brigadier looked from Benton to Liz and nodded. "Shaw, Benton. Dismissed."

"We're just getting a coffee, sergeant. Would you join us?" Liz asked, more kindly. Benton declined, and the two women carried on.

"I suppose it's safe to assume that he somehow gets that box working again, in the future," Liz commented.

"I never even knew that the TARDIS could break," Martha chuckled. "How long's he been here?"

"Oh, about four months."

"He must be going spare," Martha thought about her Doctor, who never seemed to sit still.

"I suppose. He's always tinkering on that machine of his, unless the Brigadier sends him on assignment."

"Liz, when exactly are we? Yesterday, we were in Lake District around 1900. The day before, we met a dodo. Like, the extinct bird. And then we were in 1930s Manhattan.1"

"You're not telling me that that box really is a time machine?" She shook her head. "I suppose if anyone's mad enough to invent a time machine, it would be the Doctor. It's March, the nineteenth, nineteen-seventy."

"Nineteen-seventy. I've not even been born yet, but I think this is the closest to home I've been in a long time." Martha's voice was slightly wistful, thinking of a home that did not exist. "So, what did you do before the Doctor turned up?"

"I was drafted to be UNIT's scientific advisor. When the Doctor showed up, the Brigadier recruited him and, don't tell him this, mind, since he had greater experience in the field, he took my job." Liz closed her eyes. "Or the job's been unofficially divided into junior and senior positions." Liz shrugged. "Could be worse, I suppose. They might have gotten rid of me altogether." She motioned to Martha to relate her story.

"I met him at work. The hospital was taken to the moon by space police rhinos. I'm a doctor, at least I will be if I ever take my exams," she chuckled.

"Medical, I assume?" At Martha's nod, Liz continued. "I studied medicine and physics at university, myself."

"Right, now we've got two proper doctors and two Doctors," Martha grinned. "That was really bad, wasn't it?" Liz nodded, pressing a hand against her smirk.

"Martha! Right, well, we're not going to tear a hole in the fabric of reality, and there's not a paradox. Well, not yet. Which is why we've got to go." The Doctor, Martha' Doctor, came jogging from the lab. He looked at Liz and smiled. "I hope you haven't told each other too many wild tales about me," he scratched the back of his neck.

"Well, actually, we didn't discuss you at all, did we Liz?" Martha exchanged a look with the other woman, who smirked.

"Of course not." Liz started back for the lab, followed by the Doctor and Martha.

Martha waved to Liz before stepping into the TARDIS. The Doctor put his hand on the door, turning to look at his old friends. "Oh, what the hell," he muttered. He shook his own hand, or rather, that of his younger self. "We spent all that time pretending to be old and wise, and then we were you. All racing around in Bessie and doing experiments. Can I say, Doctor, even though I didn't have the TARDIS, I loved being you. Here, look," the Doctor opened his overcoat. "Coloured linings? That's you." He grinned.

"To days yet to pass," the younger Doctor nodded, smiling, crossing his arms under his cape.

"Liz," the Doctor hugged her. "You are brilliant and don't ever let me tell you otherwise."

"Like that would happen," Liz said dryly, smirking.

"Brigadier!" His voice squeaked. The Brig raised an eyebrow. "Erhm, yes, well," the Doctor cleared his throat. A multitude of expression came over his face, too quickly to identify. The Doctor swallowed, Adam's apple bobbing. "Thank you. For everything. I never said when I was him, and, you were there when I needed you. Now, I might not have admitted it before, buuuuut," he scratched his neck, "well, anyway." The Brigadier extended his hand, smirking beneath his moustache. The Doctor, beaming, shook it heartily. "Oh, what the hell," he exclaimed, pulling the Brig in for a hug. "I might not like UNIT, but I could always count on you," he told the younger man.

He paused once more, hand on the TARDIS' door, before disappearing back into the time vortex.

1. 1. Sting of the Zygons. The Last Dodo. Evolution of the Daleks.