It was a cold and slow night in the flat, and Sherlock was bored. This seemed to be something that was happening more and more lately, mostly because no one had killed anyone for a while. At least, not in any clever way.
So Sherlock was laying on the sofa looking up at the ceiling thinking about the options to kill his boredom.
Option one; Go cause a cunning murder and then solve it to make himself seem clever. Now this option didn't appeal to Sherlock for a few reasons, the main one being murdering people was, as John puts it, "Wrong and inhumane".
Option two; Go to the mortuary and steal a head or hand to examine. He would usually find stimulating interest from random body parts of humans. It wasn't usually as pleasurable with animals...
But these options bore him even more then his prior ones. Before long, just before Sherlock got to thinking about all the different ways you could stage a murder to appear as a suicide, John unlocked the door to the flat.
"Hello Sherlock." John greeted him with a grin as he opened the door. Once he closed the door, he strode over to a chair and sat, sighing, from coming home from a long evening out.
Then, unanticipatedly, Sherlock came up with a scheme that involved John. Smirking, he stood up off the sofa, grabbed his jacket, and walked over to the door. "I'm going out. Expect me back in an hour, if you're still up." Sherlock told his flatmate.
"Where are you going this time of night?" John asked Sherlock, for it was nearly eleven pm.
"Out." Sherlock answered, sternly, and then walked out of the flat, down the stairs and into the night, leaving John clueless and a bit concerned.