Analysis of never-before-seen letters from Ian Brady and Myra Hindley, written over their five decades in prison, and personal accounts from those who knew them. 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