Emilia Fox returns for series 18 of this compelling mystery drama in five thrilling two-part stories that shine a light on the city's dizzying extremities from the rich and the poor, to the powerful and the disenfranchised. In Sniper's Nest, London is under siege from a gunman who picks off its citizens at random, and Falling Angels tells the darkly moving story of two people drawn together after they witness a man being hit by a tube train. In Protection, a young girl vanishes without trace and Squaring the Circle pitches us into classic thriller territory as the team investigate a bloody shootout. In One of our Own, the murder of a rising police star triggers an intense and harrowing journey into police loyalty and familial betrayal while the team face down a brutal gang of drug traffickers.