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.

Sure that Zezi is being held on Shetland, Perez and the team ramp up the pressure on their remaining leads. Personally, Perez finds himself in turmoil after his kiss with Alice.