Alex Galbraith is shot dead on Pérez's mother's funeral. Their investigation is interfered by Fraser Creggan. A pipeline worker Eamon Gauldie informs Pérez that he has evidence on his drone that can identify Galbraith's killer.

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

The race is on to catch Sandy's attacker before he can escape Shetland, while Lynda Morton finds herself in trouble, so she desperately calls Perez for help - offering a key name for his investigation in return. Blood from the recent break-in throws up a DNA match that leads to another murder suspect, and a shocking confession causes tensions to boil over, sowing the ...

After the shocking events of the previous night, Perez must piece together what happened before a rampaging and vengeful Creggan finds his target. Eve denies any involvement and has an alibi, while Tosh visits Maurice Ross to find out why Galbraith was paying for his care. At the religious retreat on Whalsay, Sister Carolyn receives a threatening postcard and quickly ...

Perez finds that Carrie McAndrew was in debt to Niven Guthrie. Fiona Bedford reveals that her husband is tracking her whereabouts. As Donna grows weaker, she asks Duncan for one last favor.

Niven and Darren are arrested and brought to the station for interview. Perez finally brings the investigation to a climax - but he has no time to rest when it turns out Donna has one last surprise in store.