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.