Helen Mathews is found strangled on the street. In the course of the investigation, the police learn that she was having an affair with Alan White, a flying instructor working for her husband Michael. From the evidence, it appears that she was about to leave her husband and move to Canada. The police uncover a similar case from several years earlier with a striking resemblance to this case and are convinced that the two must be connected. Friction again develops between Sam Ryan and the police when her forensic analysis demonstrates that the two cases have no connection whatsoever. Sam continues to fret over her decisions in her last case and her personal relationship with Peter Ross reaches a breaking point.

With a second murder on their hands, the police make an arrest in the case. Sam however uncovers some very peculiar bruising on both victims that provides the police with the evidence they need to identify the person responsible. Sam's life is put at risk however when the murderer threatens her. Wyn Ryan, who has been living with Sam since their mother's death, has found a job and is now looking to move on. Sam and Peter continue to struggle with their relationship but are determined to make a go of it.