Nikki and Jack head to Scotland to help earnest rural detective DS Jason Ross investigate the chilling murder of a lap dancer found in a remote forest. In their search to find a suspect, the team clash with rogue city detectives DS Mike MacNeil and DI Simon Laing. But as more human remains are unearthed in the forest, it becomes horrifyingly apparent that a dangerous serial killer is at large. News of the murders unsettles new mother Sarah, who is harbouring a dark secret from her partner Steve.

When the body of a pregnant Northern Irish girl is discovered, the team face the urgent task of finding the baby snatched from her womb. The child's father, married man Simon, is the prime suspect in DS Sally Kirchner's eyes.

Meanwhile, Thomas uncovers the teenage girl's connections to a criminal underworld. Nikki and Jack encounter her addict boyfriend Nuri and ruthless drug dealer Bekir, suspected of masterminding the killing of a Drugs Squad cop. The dead detective's partner, DI John Brooke, is out to avenge his colleague's murder.