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 racing to repair the fault, Amy must fight to continue her investigation; Kirsten's inquiries lead to tragedy.

Kirsten believes the murders were part of a coordinated attack, and her investigation takes her into the heart of Scottish politics; after she discovers a Navy cover-up, Amy questions who she can trust.

Kirsten closes in on the killer, but their capture reveals the grave threat that the Vigil faces; Amy uncovers terrifying new information about someone aboard the submarine.

Amy is trapped and running out of time; on land, Kirsten chases down the traitor's accomplice; when the traitor's plans unfold aboard the Vigil, the crew is forced to fight for their lives.