DS Tennison investigates the murder of a Bosnian Muslim woman, who was tortured and strangled.

Detective Superintendent Jane Tennison (Helen Mirren) is ripe for retirement in the eyes of her boss at the London Metropolitan Police. But it's the farthest thing from her mind as she brazenly takes over a high-profile murder case from her underling DCI Simon Finch (Ben Miles). The victim: a Bosnian Muslim woman named Samira. Injuries: torture followed by strangulation. Motive: none. Police turn up a suspect with a strange connection to the victim: Bosnian Serb Duscan Zigic (Velibor Topic), who during the Bosnian civil war spared Samira's life when ordered to kill her and her sister, Jasmina (Ingeborga Dapkunaite). Suspecting that someone gave orders for Zigic to correct this lapse, Tennison begins looking for the mastermind, worried that Jasmina might be next.