John started to notice things about a week after he moved into 221b. At first he put it down to Sherlock's many quirks, when he heard Sherlock speaking to no one in his room. Although the fact that it was usually followed by a small bang was particularly odd. Sherlock usually reserved things-that-go-bang for the kitchen.

Then there would be the fact that sometimes (not always, mind you, just sometimes) the flat would be tidier when they came back than when they had gone out, even when John had been with Sherlock the whole time. He asked Mrs. Hudson, but she a) pointed out that she was a landlady not a housekeeper, and b) that Sherlock had expressly forbidden her to ever try to tidy 221b without his express permission, and perhaps not even then.

There were the things that just appeared, you know, like the head in the fridge. How did Sherlock get them home? Especially when sometimes they would be there when John knew that Sherlock hadn't gone out. Sherlock was quite evasive about where they came from when questioned.

"Where did the life-size replica of the Blarney Stone come from, Sherlock?"

"Uh…internet? And it's not a repli— Never mind. I'm dazed because I was napping. Look, I've got a blanket."

Finally, John had had enough. He made a great show of going out and then crept back into the flat. Frankly he was surprised that Sherlock had fallen for it.

Sure enough he heard Sherlock talking to someone in his room. Actually, berating might be a better word. John crept down the short hallway.

"…and you didn't get my shoes shined in a timely manner. Do you really think that your master should go about with scuffed shoes?"

"No, Master," said a very tiny voice.

"Well, get me the Stradivarius I asked for, and we'll say no more about it."

"Yes, Master. Flummy only wants to please Master."

At that point John leapt in the room only to see a small puff and hear the bang as air rushed to fill the space where something had been.

Sherlock gaped at him for a moment, rolled his eyes a bit, sighed dramatically, ran his hands through his hair and said, "I suppose you have questions?"

"Who on earth were you talking to and why does he call you master? And where did he go?"

The voice hadn't sounded like a child, but still. Why would a 21st century man have someone in his room who called him master? John was livid. THIS should not go on in a modern Britain.

He ransacked the room, tossing Sherlock's bed sheets, shoving books and equipment aside (a golden compass?), then throwing clothes out of the closet and tapping on the back. Nothing, the back remained quite solid.

Sherlock watched and then said, "He's not here. He's gone."

"What do you mean he's gone? He can't have just disappeared!"

"Well, yes, he can. That's rather the point."

"What?"

"Can we go into the kitchen? This is…complicated, and I don't think you're going to like it."

"Oh, I'm sure I'm not going to like it. And I'm sitting facing the hall so that he can't slip out while my back is turned."

They sat in their chairs, John watching the hallway and door with his sharp-shooter eyes. He didn't want whoever it was slipping into the bathroom and getting out that way either."

Sherlock actually made tea because John wouldn't pull his eyes away from the hall. It was only right that they have tea. They were British. This could very well be a three cup problem.

"Start talking."

"His name is Flummy and…he's my…house elf."

"YOUR WHAT?"

"My house elf. He's been in the family for generations, if it's any consolation. He really doesn't want to leave, we've tried to be very fair and give him the choice. Some of the others left, but Flummy is very loyal. That's why he came with me instead of staying with Mummy and Daddy."

John licked his lips, turned his head to the side, blinked rapidly and made a face.

"He's an elf? You do realize that you're mad, right? You've gone right round the bend. You're telling me that there's an elf walking around London who…belongs to your family, and has for generations? The same elf?"

"Of course the same elf," said Sherlock impatiently, as if that should be obvious. "And anyway, he doesn't walk around London. He's a house elf."

"As opposed to the other kind, I suppose," said John sarcastically.

"Of course."

"Office block elves? Tube elves?"

"No, no, the other kind! The ones who make shoes and cookies and toys!"

John put his hand over his face and then quickly took it away, remembering he was supposed to be watching the hallway."

"Ah," cried John, thinking he had found a flaw in Sherlock's story. "If he doesn't walk around, then where did he go?"

"He disapparated to where he needed to go, to fetch what I asked for, and then he'll apparate back."

"Apparate?"

"Yes, apparate—you know—disappear in one place and appear in another? Really, John, these flaws in you education are tiring, and you berate me for not knowing the planets."

"Apparate is not a real word, Sherlock," said John, slowly and calmly. "It certainly isn't an actual thing."

Sherlock paused to look at John despairingly. It was disturbingly the same look that he generally reserved for the members of Scotland Yard. "Mycroft said you wouldn't understand."

"Oh, really? Did he? Well, you can tell your equally mad brother that I—"

Which was when there was an oomph of air being shoved out of the way and a very small, hairless, long-nosed, large-eyed being with huge pointy ears appeared (sorry apparated) on the kitchen table holding a violin. He wore what appeared to be the mate to the Union Jack pillowcase as a tunic, only it was very grubby and threadbare in places.

His enormous eyes got even wider when he saw John. He carefully laid the violin on the table and then threw himself at Sherlock's feet.

"Oh, Master," he sobbed. "Flummy didn't mean to come back when the Muggle was present. Flummy didn't feel his presence. Oh, Master, don't send Flummy away. Flummy loves Master!"

Surprisingly Sherlock reached down to gently rub the…thing's ears. "It's alright, Flummy. I'm not mad. I was telling John about you and that's why you didn't sense the Muggle barrier."

"John, this is Flummy, my house elf. Flummy, this is John. Since John lives here now and knows about your existence, I expect you to obey his wishes as well as mine."

"What? No, no. I am not ordering that…Flummy around like some sort of slave.

"Flummy," said John kneeling by the quivering…person. "Don't you want to be free to do whatever you want and go where your…people are?"

"Oh, no, Master John. Flummy lives to serve Master Sherlock and his family. Flummy would be lost without the Holmeses."

John sat back down in his chair and put his head in his hands. "This is what going mad feels like," he moaned. "I've gone mad. This is impossible and I've gone mad."

"Come, John," said Sherlock soothingly, "you know my methods. When you have eliminated the improbable, whatever remains, however impossible, must be the truth."

John gaped up at him. "I really don't think that that's the way that that should go. Surely impossible should be…I don't know…IMPOSSIBLE? That's why it's called impossible!"

"But Flummy is demonstrably here, John. He cleans and presses my clothes and tidies the flat when you're not here and gets me things I need when I can't get them…through the usual channels. Don't worry, I always have him put them back!"

"So, you are telling me," said John, slowly and calmly again, as though he didn't want to make any sudden noises and disturb his disturbed flatmate, "that magic exists and that you have access to it?"

"Well, yes," replied Sherlock as though John were finally making sense.

"You do realize that that means that your deductions are pointless, don't you? If magic exists, then a crime scene could easily be altered—by magic—to something else, something not logical at all. A would not follow B necessarily anymore."

"Oh dear," said Flummy, "I hadn't thought of that," and promptly disappeared in a puff of logic.