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.