Probing the murder of Susan Clark, Supt. Heaton visits Longmarsh Prison to speak to Ian Ellis, a man sent down 20 years ago for killing Rebecca Clayton. Ian is angry at being accused of Susan’s murder and claims that Heaton bullied him into admitting that he killed Rebecca. Meanwhile, ex-prostitute, Chrissie MacLeish, tells officers that her friend Elaine Putnam went missing a few weeks before Rebecca’s death…
When evidence proves that Susan and Rebecca’s murders are related to Elaine’s disappearance, Ian is re-arrested in prison, and brought into custody. Back at Sun Hill, Heaton holds a press conference, where Ian’s brother, David, rages that Ian is the victim of miscarriage of justice: he’s no killer. Later, Heaton learns that evidence regarding Rebecca’s case was kept hidden by officers at the time.
Heaton talks to his former DCI Ted Ackroyd, who admits there was a cover-up in Rebecca’s case, prompting Heaton to doubt Ian’s murder conviction. Elaine’s body is soon found and when forensics confirm she was killed in the same way as Rebecca and Susan and that Rebecca knew Ian’s brother David, he is brought in for questioning, where he reacts with fury when accused of being involved in all three murders.
While David accuses Heaton of making things up as he goes along, a desperate Ian tells Heaton he’s been robbed of his freedom. Later, Heaton rushes to the custody cells to find that Ian has tried to kill himself.