The first episode features an eyewitness account of the last murder from Myra Hindley's brother-in-law David Smith, and contributions from 1960s pop singer Janie Jones, who befriended Hindley in prison and conducted a 40-year-long correspondence with both Hindley and Brady.

In 1966 Brady and Hindley are brought to court. Eyewitnesses describe the trial, as letters reveal the serial killers' carceral after lives as Britain's longest serving prisoners.