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 a trace, and Squaring the Circle pitches into classic thriller territory as the team investigates a bloody shootout. In One of Our Own, the murder of a rising police star triggers an intense and harrowing journey into police loyalty.