A man is killed in an apparently random attack, and suspicion falls on a gang of muggers. Only Detective Sergeant Geraldine Steel thinks this is the work of a more deliberate murderer. Two more victims are discovered, after further seemingly indiscriminate attacks, and this time the muggers have a concrete alibi. All the while the killer remains at large. When Geraldine finally manages to track down a witness, she finds her own life is in danger..