In the aftermath of the diving incident, the team searches for a link between the two bodies. Meanwhile, Perez must deal with the return of Donna Killick.

The hunt is on for Sandy's attacker, before a shocking confession causes tensions to boil over and some Islanders take justice into their own hands.

After the shocking events of the previous night, Perez must piece together what happened before a rampaging and vengeful Creggan finds his target.

Facing a dead end in the hunt for Galbraith’s killer, Tosh leads Perez to the remote island of Fetlar. Donna asks Duncan for one last favour.

As Perez closes in on the identity of Galbraith’s killer, he struggles with Duncan’s secret, while Donna has one more surprise in store.