[HarryT]

Sparrow,

Spoiler:

This is one of the many things I was referring to when I said that it paid homage to the original. It's a joke put there for fans of the original story. In the original, Lestrade sees the word "Rache" written on the wall, and thinks that the victim was trying to write "Rachel", and hence goes off looking for a woman of that name, until Holmes points out that "Rache" is the German word for "revenge". Here, Lestrade thinks it means "Revenge", but Holmes realises that she had been trying to write "Rachel".