DI Costello faces a disturbing child abduction case; a six-week-old has been stolen and replaced with another baby. The swap took cold and meticulous planning, so Costello treads the seedy, Glaswegian backstreets for answers. She's convinced that more than one young life is at stake. Promoted into the Cold Case Unit, Colin Anderson reviews the unsolved rape of a young mother, whose attacker is still out there. Each case pulls Anderson and Costello in the same direction and, as their paths keep crossing, they begin to suspect their separate cases are dangerously entwined.