Scar
It was a rainy day and Holmes and I sat in our living room at Baker Street. There had been an absence of cases recently and due to this lack of activity, I thought it an appropriate time to ask,
"Holmes, wherever did you get that scar behind your ear?"
Holmes smiled ruefully and rubbed at the thin, pink line. It was barely noticeable, but I had been wondering about it for some time.
"Ah yes," he said. "Well Watson, it was a few years before I met you and… I went out to a tavern with a few of the inspectors, the regular lot; Gregson, Lestrade and so on, as well as a few others… and…"
"And?" I prompted eagerly.
"And I hadn't realised that they would be angry drunks…"