Harry Pearce finds himself in front of a tribunal over his willingness to trade the Albany file to save Ruth Evershed but he is temporarily reinstated at the request of the Home Secretary. Erin Watts had replaced him while he was on 8 weeks of enforced leave and he is pleased to hear she is to stay on as Section Chief. On his return he learns that a one-time agent, codename Sharecropper, had been trying to get in touch with him. Unfortunately, he was murdered just 72 hours before his return. Elena Gavrik, codename Tourmaline, is the wife of a Russian minister and was one of their best sources of information during the cold war. Harry thinks Sharecropper was trying to tell him that Gavrik is in danger of being exposed. For Harry however, Tourmaline is more than just another ex-agent.