Whispers Under Ground

Whispers Under Ground is the third novel in the Peter Grant series by English author Ben Aaronovitch, published 2012 by Gollancz.

Peter Grant of Metropolitan Police department in charge of magical crimes (AKA The Folly) is called in to assist in a murder investigation. The victim, an American student found stabbed to death at Baker Street station was killed with a pot shard, raising the suspicion the death may be Falcon (police code for 'Folly') related. It quickly emerges that there is not merely a supernatural component to the case but that a secret world lies beneath the streets of the 'mundane' (non-magical) metropolis, and that the supernatural semi-human subterranean inhabitants may be no more harmless than the entirely human population who are blissfully unaware of their existence.