(A/N: So... not a lot of "enchanted," more "echo," though "enchanted" is certainly there in subtext. But I did find a more active tone finally and I'm really pleased with this one, so yay!)

E: Echo/Enchanted

"What did you say?"

Sherlock, comfortably ensconced in the couch, looked up in surprise. John, reading a magazine in his chair by the fire, was giving him a strange look. "I said you're wrong," Sherlock repeated.

"How can I be wrong?" John said. "I haven't said anything. Or done anything."

"You just said she wouldn't have given her brother a key to the flat because they didn't get along. But someone recently arrived to the city-"

"Sherlock, I didn't say anything." John's expression was split between alarm and concern; also the wrinkle in his forehead that meant he was thinking. No doubt mentally dusting off his medical training and sorting through the potential causes of auditory hallucinations. Sherlock found the explanation much faster. "Ah. It wasn't you, then; I must have been talking to the you that I talk to when you aren't here." Sherlock frowned. "But you are here."

John may or may not have answered; Sherlock wasn't paying attention anymore. He went into his mind palace. Currently it looked like 221 B Baker Street, because he had been accessing things that he kept there. The resemblance was perfect-down to a Mind Palace John sitting exactly where Real John was sitting, in his armchair. "What are you doing here?" Sherlock asked, perplexed.

"I live here, you berk," Mind Palace John said.

"No you don't. Nobody lives here. I came here to access the the file on lockpicking, I don't need you for that." He must have accidentally pulled John up to bounce ideas off of while he was looking for the file, but it was unnerving that he hadn't realized it. "Get out, John."

"Excuse me?"

Sherlock blinked, feeling a headache coming on. He must have spoken out loud again; it was Real John who had answered him, and with a certain level of indignation at that. "Not you!"

"Then who are you talking to?!" John's eyes narrowed in suspicion. "You didn't rename the skull, did you?"

"I told you, I'm talking to the you that I talk to when you're not here. In my mind palace."

"You mean you actually made a copy of me in your mind palace?" John asked, seeming mildly surprised. "I always thought you just didn't notice whether I was here or not."

"That's ridiculous, of course I notice."

John frowned. "Then how is it you can't remember I don't actually know the things you've said to yourself in your mind palace while I'm not here?"

"Well I can't be expected to keep the two of you straight! Now keep quiet, it's very irritating talking to both of you at once." Sherlock closed his eyes, even though he could easily access the mind palace with his eyes open, hoping it would deter Real John from talking.

It would have been much less disconcerting going back and forth if Mind Palace John and Real John hadn't been sitting in exactly the same place. But Mind Palace John did not have a magazine; also, he was waiting to talk to Sherlock with an expression of easy confidence, while Real John was starting to get in a huff. "Now, what did you mean you live here?" Sherlock said to Mind Palace John. "No one lives here."

"No? Awful crowded in that case. Mycroft's here nearly every day."

"How do you-never mind, that's not the point. I pull people up in here, just like any other information, when I'm working on a specific problem that I need to hear their voice on. When I don't need them anymore I put them away."

"Well, maybe you need me all the time."

"Impossible."

Real John interjected. "You do realize you're mumbling to yourself over there, don't you? What's impossible?"

"What?" Sherlock exclaimed, opening his eyes. "Oh, for heaven's sake, stop interrupting!"

"Interrupting a man's conversation with himself," Real John muttered.

"It's not with myself, it's with you. Not you-you, Mind Palace you."

John tossed his magazine onto the side table and stood up, irritation and exasperation written in every line of his face. "Why are you arguing with some pretend version of me in your head when we're sitting next to each other?"

"Because I don't know why you're there. Now will you please shut up?"

Real John didn't say anything else. Sherlock closed his eyes again, and found Mind Palace John still in the armchair. "Stubborn, are we?" Mind Palace John said.

"I didn't consciously leave you here," Sherlock told him.

"Nah. And Sherlock Holmes never does anything subconsciously."

"No, I do not. At least not in here."

"You just prefer to think out loud, and you don't like doing it to an empty room. I don't draw as many strange looks as the skull."

"Yes. That's it," Sherlock said, feeling the pieces of the puzzle connect. John's function as "person who listens" must have been so strongly ingrained on Sherlock's brain that John had popped up when Sherlock hadn't meant to bring him, just because Sherlock was mulling things over.

Mind Palace John shook his head. "Sherlock, has it ever occurred to you that saying 'I like to talk, and I prefer for a person to be there when I do' is the same as saying 'I'm lonely, will you listen to me?'"

"...No, it hasn't."

"You probably think my being here all the time is some big mystery, or an error you need to correct. I'm here because you're lonely. I will always be here, because you will always want someone to listen to you and believe you, even in the privacy of your own mind. I won't get in the way of your all-important Work. I'll just be here. Specifically, right now, in my room. Because I believe you have something else to do."

Mind Palace John unfolded himself from his armchair and strolled out of the room. Sherlock sat there for a moment, staring at his own knees, before leaving the mind palace. It was really very disconcerting, everything being so very much the same; only Real John was now at the table, typing on his laptop. Possibly a passive-aggressive blog about his not-entirely-sane flatmate. When he noticed Sherlock watching him, Real John asked, "Did we have a row? You and fake me?"

"No."

John looked back at what he was typing. After a moment he noticed Sherlock was still watching him. "What? You have something you want to say to the real me instead of talking to yourself?"

A mental voice whispered, The same as saying 'I'm lonely.' "Yes."

"...So what it is then?"

"I don't know yet. Give me a minute. I'll think of something."