"I find myself confused," the Doctor said.
"My friend Watson is more so," Holmes replied. "While checking your pulse -"
"Oh yes, that," the Doctor said with a casual wave. "Two hearts, double heartbeat, and there's a respiratory bypass system and a good many other anatomical differences while we're at it. Well done him for noticing it."
Holmes frowned. "More of an anomaly, to my mind, is your clothing and other belongings."
The Doctor sat up sharply. "Am I to understand that you've been going through my pockets?"
"Certainly not," Holmes said, a little too hastily. "I am not even referring to the style of your clothing. I am referring to the fabrics from which it is made."
"I'm glad to hear you aren't dissing the bowtie," the Doctor said. "Bowties are -"
"Yes, yes, they are positively cool, whatever that may mean. You have informed me of this three times already." Holmes stared at the Doctor thoughtfully. His cup of tea lay neglected in his hands. "So. A person who appears human but whose anatomy is decidedly non-human, wearing clothes of a style not suited to the place and time, made from fabrics which quite simply do not exist, and using an argot with which I am not familiar. I might suppose myself to be in one of Mr Wells' scientific romances."
"But you know you aren't, don't you?" the Doctor said softly. "You know that your observations are correct."
Holmes focused a glare on him. "How am I supposed to make any sort of reasonable deduction based on these premises? I work with data, sir, but the data which you offer makes no sense!"
"Let me propose another way of considering it," the Doctor said, pouring himself tea. "The data which I offer makes no sense because you are not informed about this particular data. If I were to give you mud from a particular London street, you would be able to analyse it and tell me all about it in more detail than any sane man could possibly - that is, you would be fully informed on the subject. But if I were to give you mud from Mars, well, what do you know about Mars?"
"Only that the canali or canals fail to actually indicate intelligent life," Holmes said stiffly. "And certain astrological references that have been included in the beliefs of some serial killers and frauds of my acquaintance. Otherwise I find it of little interest, as it has nothing to do with my work."
"Ahhh." The Doctor sniffed the tea and added several sugar cubes. They splashed in dramatically, then floated to the surface, slowly turning brown and crumbling. "But how do you know that it will not have any bearing on your work in the future? How do you know that you won't run into some sort of clue that you would recognise if only you'd known that, oh, say, that Ice Warriors dislike the heat?"
"Ice Warriors?" Holmes queried.
"The - wait, at the moment they'd be in suspended animation. Trust me when I say that I don't think you will meet them. But the question holds, doesn't it? How do you know what you'll need to know?"
Holmes looked away. "The function of research," he snapped. "No man can know everything. We can only stock our minds with the most likely knowledge. What is the likelihood that I will need to know the orbit of Mars, compared with the need to know the gangs of London? And what precisely are these Ice Warriors?"
"Look, forget the Ice Warriors for a moment," the Doctor said. "They're generally very reasonable types and their moral system is analogous to the human one in enough ways for polite interaction, assuming you don't go invading each other as much as you're going to. I don't know. You lot and Ice Warriors and Silurians and -" He sighed. "I wouldn't mind so much if - well, actually, I would mind so much and I do mind so much. You lot."
"You confirm my hypothesis about your alien nature," Holmes said with great satisfaction.
"As long as it takes you off the Ice Warriors, that's great," the Doctor said. "But we were talking about relevant information, weren't we?"
"By that token," Holmes said, "what do you consider to be relevant information? Something concerning alien planets such as your own? Your reference to Mars and to the Ice Warriors -"
"The Ice Warriors have nothing to do with it!" the Doctor said. "Forget about the Ice Warriors! Let them go! Talk about something other than Ice Warriors! They're taller than you anyhow and they're green!"
"Does that mean a chlorophyll component to their metabolism?" Holmes asked curiously. "Assuming that Mars' waters are ice-bound, as some scientists have hypothesised, perhaps some sort of plant creature could be assumed. Indeed -"
The Doctor took a long and noisy slurp of tea. "Relevant information," he said loudly. "Why yes, I do indeed keep myself well-informed about alien races, including those such as your own - and I refer to humans here, native to the planet Earth. Very useful to a traveller like myself, especially knowing the dates for when an invasion's scheduled -"
"Not the Ice Warriors! They don't show up till - anyhow, what I am trying to say is that one needs to remember relevant information such as this and local customs. One does not wish to give offence. May I have some more of that excellent sugar?"
Holmes stared at him with the cool regard of a snake. "You are attempting to convince me that your recall of local customs is in fact incorrect and thus that you are amusingly harmless. You are very well aware that it is tea that one drinks, and that sugar is an addition."
"Oh well," the Doctor said. "Can't blame me for trying. And to be honest, it is a bit of a problem keeping track of everything. I tend to reprioritise every now and again."
"How often?" Holmes asked.
"Hm." The Doctor checked his watch. "Ten times so far. I come to a life-changing sort of situation, and I find my priorities tend to shift a bit. One day I'm all up on Roman art and dentistry, the next I'm more into Venusian Aikido and wine-tasting. Sometimes I can play the spoons - and let me tell you, I play a mean spoon - and other times I'm more pro-recorder. Seriously, have you any idea how many brain cells I need just to keep up on the relevant information about tea?"
Holmes' brown furrowed. "So you actually do prioritise information."
"Well," the Doctor said. "Tea's important. So are Ice Warriors. And ducks. And for some reason I have a strong feeling that it's going to be very necessary to keep up to date on mobile phones, prisons, paintings, and the quality of silence, not to mention mountain-climbing. Now that's something which never goes out of fashion. Speaking of which, would you mind if I borrow a few dozen metres of rope before I go? I need to get at the library."
"I assure you, Doctor, there are a number of libraries in London, and to the best of my knowledge none of them require rope to be admitted."
"It's the one in my TARDIS," the Doctor said, tapping his nose meaningfully. "There was a little accident with some water, and I think it's going to take more than a quick go-over with the hairdryer."
Holmes settled back in his chair with a sigh. "Once again, Doctor, you go beyond the realms of my known data and established facts."
"Just think of me as fictional," the Doctor said cheerfully. "After all, if one of us knows he's real, then the other one must logically be a story."
"I suppose that is some reassurance," Holmes said. "Watson would no doubt agree. But I would prefer to think of it as a matter requiring some research."
"Oh dear," the Doctor said, and made a mental note to avoid Victorian London for a while.