A severed hand washes up on a Shetland beach, with further body parts discovered in a holdall that has been dumped at sea. Perez and the team begin a complex murder investigation.

A horrifying discovery at the Hayes house changes the course of the investigation. Perez establishes the probable cause for Daniel's murder and his sister Zezi's disappearance.

Sandy feels the heat in the aftermath of Calum’s suicide. Convinced that McGuire is the key to cracking the case, Perez travels to Glasgow in an attempt to track him down.