Boxer Kevin Sharma dies from blows received in the ring, but pathologist Sam Ryan determines that he has a brain injury dating from sometime after his last bout two months ago. One of the governors of the boxing board, retired police Superintendent Jack Reeve, is concerned that it will reflect badly on them. Reeve is also trying to cancel one-time trainer Terence Cross' license after he is the victim of a hit and run accident that leaves him a quadriplegic. A new Detective Superintendent, Peter Ross, is now in charge and Sam and he knew each other many years previously. Trevor finds himself alone after his wife leaves him. Sam and her sister Wyn bury their mother

The investigation continues and a boxing trainer apparently commits suicide. Sam isn't convinced however and with the assistance of a ballistics expert, obtains the evidence to prove the suicide was actually murder. She also learns the reason for Kevin Sharma getting into a bare-knuckles fight and now suspects that Terence Cross' hit and run may not have been an accident. Sam's sister Wyn continues to have difficulty coping following the death of their mother.

Stuart Evans is 40 years old and in the advanced stages of AIDS. When he dies the night after his birthday party no one thinks anything of it but his parents donate his remains to scientific study. When Sam and Trevor start an examination of the remains, they notice needle marks and suspect his death may not have been straightforward. Their suspicions are confirmed when the toxicology reports indicate an extremely high level of morphine. Mark Tate is also an AIDS sufferer who has been told that he will soon go blind. He too dies suddenly and when the police learn that he and Evans had the same physician, they begin to suspect doctor-assisted suicide.

As Sam continues her forensic investigation into the two deaths, the police make an arrest but soon realize they have the wrong person in custody when a crucial piece of evidence is uncovered. Sam discovers the true identity of the person behind the deaths but rather than tell the police, she decides to let him to turn himself in. Unfortunately, this leads to a tragic result. In her personal life, Sam and Peter Ross renew their long-ago romance.

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.

When 72-year old Millicent Lockwood is found brutally beaten to death in a local park, the police immediately focus on a local who was seen arguing with her a short time earlier. The autopsy reveals little evidence but Sam Ryan once again refuses to make the evidence they do have fit the suspect, which leads to an inevitable clash with the police. She also sees two youths, Kelvin Price and Ben Quayle, act out part of the murder. The police however are pursuing other lines of inquiry and don't have the time, nor the inclination, to pursue Sam's theories. She then sets off on her own investigation.

Convinced that Kelvin and Ben are the murderers, Sam Ryan pursues her own investigation. She is also concerned that one of the boys may do himself harm after a third boy, who was only peripherally involved, hangs himself. The police are concerned that her involvement may actually taint some of the evidence they have and an angry DCI Peter Ross informs her that he has filed a formal complaint with the Coroner and the Chief Constable over her conduct. This obviously affects their professional and personal relationship.