The North East, 1970. On the brink of retirement, DCI Gently and his team investigate a body found in a chemical waste tank. When Gently discovers the victim's wife was convicted of the murder eight years ago, he decides to re-open the case - a controversial move. But DI Bacchus opposes Gently's decision, not least because he worked as a DS on the original investigation - putting mentor and protege at complete odds. Is Gently about to expose an appalling miscarriage of justice, or will he sacrifice his reputation and legacy for a convicted murderer? And can Rachel help heal the widening rift between her superiors, whilst navigating being a woman in a professional male world? Finally, will the team finally prove beyond doubt the identity of the killer?

The Old Bailey, London, 1970. Gently is bowing out of the force on a professional high when he is approached by a covert anti-corruption police unit with one last tantalizing job: the cold case of a young girl murdered four years ago in new town Washington, County Durham. The investigation finds Gently tracking MP Michael Clements, a charismatic politician who fearlessly pursues political reform in the North, promotes ever-closer links to Europe, and who is tipped to be a future Labour Prime Minister. When the investigation leads to a murky web of union and political intrigue, placing Bacchus and Rachel in danger, will Gently do the unthinkable and bend the course of justice? How can Bacchus and Gently repair their frosty relationship - and faced with mortal danger, how will Gently and his team survive?