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.

The discovery of Niki’s body intensifies the search for Zezi. Perez feels that time is running out. A desperate Olivia tries to get information from Jamie Hayes.

Perez closes in on Zezi's location at last. But can he reach her before it's too late?