Rabbit Hole by Mark Billingham

They were meant to be safe on Fleet Ward: psychiatric patients monitored, treated, cared for. But now one of their number is found murdered, and the accusations begin to fly. Was it one of his fellow patients? A member of staff? Or did someone come in from the outside?

DC Alice Armitage is methodical, tireless, and she's quickly on the trail of the killer.

The only problem is, Alice is a patient too.