What Original Story Is This?

[lostwiginity.livejournal.com]

I don't remember what ACD story this scenario is from.

Holmes comes home (or to a shared hotel room, I dunno), and asks Watson if he would be alarmed to be near/share close quarters with a madman, or something along those lines. Watson is confused and answers in the negative. Holmes seems satisfied by this, and I think that's when the conversation ends.