The Doctor made a final scan of the auxiliary quantum capacitor module with a swipe of his sonic screwdriver. It made a pleasing whirring noise.
"Well," he chirped. "Everything seems to be in working order. But I guess that's pretty obvious, really. If it wasn't, we probably would have asphyxiated by now. Or something like that."
He paused, and waved his hand a fraction in the direction of the brooding man nestled in the corner. There was no reaction.
"Or we might have exploded. The TARDIS explodes a lot more frequently than people might think. And explosions aren't any fun at all. Well, not when you're in the middle of them," said the Doctor. "That happens quite a lot too. Would you like a cup of tea? I've got a brew on. And biscuits. Might be a bit chewy though. Picked them up back in the 1950s. Helped a charming young lady deal with a nasty Cyberman problem, and I got cookies. Pretty good deal, I'd say."
"I am thinking," the brooding man glared into middle distance. "Shut up."
"So I noticed," the Doctor smiled. "You're quite the thinker. Lots of stuff up there," he said, tapping his temple. "You guessed the TARDIS was, as you put it, a 'time machine'. In a single glance! Most people are still trying to work out what that means even after I've explained it. That's pretty impressive stuff. Unless we've met before, that is. Have we met before?"
"No, we haven't," the man snapped. "And for your information, I am not 'most people'. Now shut up."
The Doctor chuckled and produced a cookie from his jacket pocket. He tossed it in his mouth, still grinning to himself. "Any more outbursts like that and we might not have enough room in here for both our egos." He produced another cookie and trotted over to the man in the coat. He tapped him on the shoulder with the biscuit. "And by the way - what's wrong with being 'most people', eh? They're fascinating things. Quite remarkable in little ways. Very... persistent."
The broody man turned and glowered at him. "Do you ever shut up?"
"Not really, no," the Doctor said. He brandished the cookie at his guest. "Hungry?"
"Shut up." The cookie was swatted from his hand and danced across the floor. "Shut up."
"Moody." The Doctor's eyes lit up. "But I guess this is all a bit much for you. You're a clever man - anyone can tell that - but you're not very elastic when it comes to thinking outside your little box. You're from... what, twentieth, twenty-first century Earth? Years and years before you guys discover time travel."
The man in the coat looked furious.
"But you're not going to let a little thing like impossible science stop you, are you? See, I knew I liked you when you came in! Oh, I like this. You're fantastic, you are. Brilliant!" The Doctor clapped and rubbed his hands together, twirling away on his heels. "You're working it all out. Just because you've never encountered time travel doesn't mean you're going to let it beat you. You're going to unravel this even if it kills you. You're like me! Only not quite as handsome."
More glaring. The man in the coat was very good at glaring.
"Sorry about that," he said. "But it's fascinating, really. Even though all this," he spread out his arms at the whirring, beautiful mess that was the TARDIS, "is completely beyond your comfort zone, you're working it all out. You don't need to ask questions because you're finding all the answers in your head! So... so go on then. What have you got so far? Ooh, this feels kind of like a test. I feel like a teacher. Haven't done that in a while - "
The man's fist connected with his jaw, sending him sprawling across the floor.
"Ow. That hurt."
The man in the coat stepped up to him and loomed overhead.
"This is a time machine," he growled. "A vehicle that's larger on the inside than it outwardly appears, and can be rendered invisible."
"Good, good. How'd you work that out?"
The man sneered. "The dimensions of this room alone is too large to fit in the approximate space that I had left to fall. Also, as I descended, I couldn't see the craft until I was inside it."
The Doctor nodded. "What about the time machine part?"
The man in the coat seemed to ignore him, and continued. "You're a renegade alien who commandeered the time machine illegally." As the Doctor opened his mouth to speak, he hurriedly explained. "Though you look and superficially act like a human, your reactions, mannerisms and... choice of clothes imply a very different cultural experience to anything Earth has to offer. You're practically a walking cartoon character.
"The craft has clearly been shoddily repaired multiple times, in a way that the original designers didn't intend - obviously it hasn't been touched by an actual professional with certified experience in maintaining it for a very long time. Any normal person who had damaged such a valuable form of transport wouldn't risk trying to repair it by themselves, or leave it in the hands of the inexperienced. You clearly don't want to contact any officials with more knowledge in that field for some reason. A criminal doesn't want to return the things they've stolen."
"Impressive. Good reasoning," said the Doctor. "But the TARDIS is borrowed. Not stolen. There's a very distinct difference."
The man in the coat seemed amused at that. There was something in his expression, something in that demeanour and that curious way he seemed to work everything out so seamlessly that was oddly familiar to the Doctor, but he was struggling to remember who the man reminded him of. Himself excluded, of course.
"As for my presence here," the familiar man continued with a tone that dripped with sarcasm, "let me guess - you've lost your pet Martian, or the moon's disappeared and you need my help to find it again."
The Doctor wrinkled his nose. "Which moon?"
There were no words uttered for several long seconds. "THE moon," The man spluttered, as though this explained anything. Spying the incredulous expression spreading across his host's face, however, the man's cheeks flushed a slight shade of pink. "Shut up."
"Anyway," the Doctor smiled genially and dipped his hand back into his pocket, slightly disappointed to discover that nothing but the crumbs of cookies long since gone remained. "You did very well. B plus, have a gold star or something. You got every point absolutely one hundred percent correct. Except for the whole 'needing your help to find the moon' thing. Actually, the whole moon situation was a bit wrong, but I'll let you off, because I'm nice."
The man sighed. "I didn't actually mean you wanted me to help you find the moon," he said. "How do I put it in a way you could understand? You want me to help you solve a problem. That's why you brought me here."
"Only I didn't. It was an accident. Pure coincidence," the Doctor said. He took his sonic screwdriver firmly in hand and twirled around in his fingers. He pressed it, and it made the little whirring noise again.
"I don't believe in coincidence," the man grumbled.
"Nor do I," the Doctor chuckled, gazing at the little green light emanating from his screwdriver. "On a completely unrelated and terribly unimportant note, I never did catch your name."
Clearly unimpressed at the sudden drop in intelligent conversation, the man rolled his eyes. "Sherlock Holmes. Consulting detective."
"That's it!" The Doctor hopped into the air and scuttled away to the TARDIS control panel. He pulled a few levers, flipped a dozen or so switches and watched as his wonderful blue box roared and shuddered to life. "I knew it!"
"Knew what? What on earth are you talking about?" Sherlock Holmes was nearly knocked off his feet as the TARDIS rumbled all around them.
"You! I thought I knew you. There was something about you I was sure I knew, and I didn't know what, but then I scanned your bio-readings and it came up with a match. A match! You share a key genetic strand with someone I've met before. But you don't just share it. Oh no, it's identical. It's exactly, exactly the same. Oh, it's uncanny," the Doctor giggled, flipping yet more switches, turning cranks, pressing buttons. "It's practically impossible."
Sherlock's eyebrows raised. "You mean to say there's another Sherlock Holmes out there?"
"Quite the coincidence, wouldn't you say?"
Both Sherlock and the Doctor grinned.