Vigil

When a crew member is found dead onboard the Trident nuclear submarine HMS Vigil, the Scottish Police are called on to investigate. The catch? The UK's nuclear deterrent must remain unbroken, so the submarine stays on patrol and Detective Chief Inspector Amy Silva must go aboard to investigate.

Although the death has been written off as an accidental overdose, Amy suspects foul play. But the crew close ranks in the face of Amy's questioning, and a new threat overshadows her inquiry.

Vigil's reactor shutdown leaves the submarine exposed and the crew racing to repair the fault. Kirsten uncovers a feud among the Vigil crewmates, leading Amy to question whether her investigation has been deliberately obstructed. A hard-won breakthrough leads Amy to believe she finally has the killer in her sights, only for surprising new evidence to cast doubt on her theory. On land, Kirsten's investigation leads 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 starts to question who she can trust on Vigil, when a message from Kirsten makes her realise she is being deliberately undermined.
 

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 and has concerns that they are orchestrating a cover up. Amy uncovers terrifying new information about someone aboard Vigil. Kirsten closes in on the killer, but their capture reveals the grave threat that Vigil faces.

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, but with no word from the boat, she fears for Amy's safety. Amy's quest to uncover the truth places her in grave danger.

Amy is trapped and running out of time, but will assistance arrive too late? On land, Kirsten chases down the traitor's accomplice. When the traitor on Vigil puts their plans into action, the crew are forced to fight for their lives.