Ricochet - Paula Gosling

When Professor Mayhew is murdered in her own home, Jack Stryker's team believe they are investigating a straightforward case of domestic homicide. Jack, however, has his doubts, though he isn't sure whether his uncertain frame of mind is due to the case or the fact that his relationship with Kate Trevorne is going through a rocky patch. Kate, meanwhile, has been receiving a series of unpleasant and anonymous phone calls at her department in the university. Too proud and stubborn to ask Jack for professional help, she decides to trace the caller herself. Then a student of the dead professor is murdered in an unsavoury part of town while he was working his shift as porter in the hospital's emergency department. It could have been a mugging which went too far, except that a few hours beforehand he had called the police station and spoken to Jack in some distress.
What possible motive could link the two killings, and is Kate's refusal to tell Jack about the phone calls preventing him from knowing all the facts?

Another blissfully serpentine mystery from the mistress of the genre.