The final episode of the detective drama sees Gently testifying against corrupt Met officers as he prepares to retire from the force. However, he is persuaded to take on one final investigation - re-opening the case of a woman who was murdered four years previously. Gently's search for the truth leads him to investigate a reforming politician who is tipped to become the next prime minister and uncover a web of political intrigue that places Bacchus and Rachel in danger. Starring Martin Shaw, Lee Ingleby and Lisa McGrillis.