Vigil

When a crew member's death on the Trident nuclear submarine HMS Vigil is written off as an accidental overdose, Detective Amy Silva boards the vessel to investigate suspicions of foul play.

When the Vigil's reactor shutdown leaves the submarine exposed and the crew scrambling to repair the fault, Amy must fight to continue her investigation. Meanwhile, Kirsten's inquiries lead to tragedy.

Kirsten believes the murders were part of a coordinated attack. Her investigation takes her into the heart of Scottish politics and the naval cover-up of a near catastrophe in the US.

Amy confronts one of the crew with her discoveries about their deception, but with her mental health suffering, questions are asked about her fitness to investigate; on land, Kirsten refuses to bow to pressure from the authorities.

Vigil is forced into lockdown as disaster strikes. With hostile boats tracking the submarine, and communications down, Vigil's crew have to navigate this crisis alone. Kirsten desperately hunts for clues to reveal the source of the threat to Vigil.

Amy is trapped and running out of time; on land, Kirsten chases down the traitor's accomplice. When the traitor puts their plans into action, the crew are forced to fight for their lives.