"What're you looking at so intently in there?" John sidles over to where Sherlock's peering keenly into his microscope before leaning down to scratch the irritated red spots on his calf.
Sherlock's response is mumbled and unintelligible. He's talking out of the side of his mouth.
"Pardon?"
"Bedbugs?"
John pulls away. "Oh god, Sherlock. Why did you bring a bedbug into the flat?"
"It seems to have showed up of its own accord. With friends."
The sudden realisation dawns on John as he looks down at what he thought had been a rash on his leg.
"Oh Christ. We have bedbugs. WHY do we have bedbugs?"
Sherlock looks sheepishly down into the microscope to avoid further conversation.
"It was that disgusting hotel you insisted we check into in Glasgow, wasn't it? The one with the owner with the weird upper lip."
"I needed to be sure he was the man we were tracking down, John!"
John groans, rolling his eyes and sitting in one of the kitchen chairs, scratching his legs all the while. Sherlock seems entirely unbothered - of course he's found a way to ignore it, if he's even been bitten at all.
"This is your fault, Sherlock, you can hire someone to take care of it. You insisted on staying in that hovel, and now we have bedbugs."