The series tells the story of the last woman hanged in the United Kingdom. Ruth Ellis is arrested after the shooting of her lover, David Blakely. She confesses to murder, and the police believe it's a foregone conclusion. But Ruth's lawyer, John Bickford, begins to understand what she's been through. As Bickford tries to understand how love turned to murder and realizes there's more to David's death than meets the eye, he wonders what Ruth is hiding and why.