Upon a Dark Night — Peter Lovesey

A young woman is dumped, injured and unconscious, in a private hospital's parking lot. She is an amnesiac with no memory prior to her discovery by hospital personnel. Detective Inspector Peter Diamond of the Bath homicide squad is unwilling to become involved. He has other, more important cases to solve: A woman has plunged to her death from the roof of a local landmark while half the young people of Bath partied below, and an elderly farmer has shot himself. Are these apparent suicides really so, or are there sinister forces at work? And then he finds a connection to the amnesiac woman named, temporarily, Rose.