Full Dark House by Christopher Fowler

Early in the morning, on the second Tuesday in September, an explosion destroys the headquarters of the London Metropolitan Police’s Peculiar Crime Unit killing Arthur Bryant one of the unit’s senior detectives; leaving his partner John May to sift through the debris and to find out why. The only clues lead back to the duo’s first case, the gruesome mutilation of a young dancer during the London Blitz. Why after so many years is the ghost of this case coming back to haunt May. What does this have to do with Bryant’s murder. Has the murderer they thought put to rest come back to kill again?