A scientist is found dead in the bird observatory on Fair Isle, Perez's childhood home, so he takes Tosh and makes his way across to the island, where he is greeted by his father - just before flights are grounded by incoming storms. Working alone and without a forensic team, the detectives talk to the victim's friends, family and colleagues - and as tensions run high, the storm forces Perez and the suspects to remain together under a single roof.