Whodunnit?

CRACKFIC! Now that THE CONCERT episode has aired in the US, I'm reposting this drabble independently. It was originally in my Chelsie drabble collection, but there is no Chelsie here, so... SEASON 4, EPISODE 3(UK) or 2(US) SPOILERS. I wrote this because I needed some humor in my life after seeing the episode.