Peter Manuel, recently released from a nine-year prison term for a series of sexual assaults, is determined to make Detective William Muncie - the man responsible for his incarceration - pay the price. After a further sexual attack on a young woman named Mary McLauchlan, Manuel elects to defend himself in court and manages to secure a not-proven verdict. Muncie promises a distraught Mary that he will not rest until Manuel is behind bars.

Nine months after the death of Anne Kneilands, the police are no further forward in finding her killer, although Detective William Muncie is sure he knows the culprit. Even though not part of the investigation, he goes to Peter Manuel's home to try and reason with his father who gave him the alibi he needed to be free from police suspicion. Then Muncie hears the news that three women in the Watt family have been shot dead in their beds. The husband William, who was on a fishing trip at the time, is arrested. However, Muncie is convinced Manuel is the man behind all four murders.