The mysterious disappearance of a Scottish fishing trawler and a death onboard a Trident nuclear submarine bring the police into conflict with the Navy and British security services.
Cast:Suranne Jones , Rose Leslie , Shaun Evans , Paterson Joseph , Adam James , Connor Swindells , Gary Lewis , Lolita Chakrabarti , Anjli Mohindra , Lorne MacFadyen , Stephen Dillane , Lois Chimimba , Bobby Rainsbury , Cristian Ortega , Martin Compston , Daniel Portman , Tom Gill , Anita Vettesse
When a crew member is found dead aboard the Trident nuclear submarine HMS Vigil, DCI Amy Silva is flown out to investigate.
With Vigil in danger, Amy must fight to continue her investigation. Meanwhile, Kirsten's enquiries lead to tragedy.
Kirsten's investigation takes her into the heart of Scottish politics, but when she unearths a navy cover-up, it leaves Amy questioning who she can trust on Vigil.
Kirsten closes in on the killer, but their capture reveals the grave threat that Vigil faces. On the submarine, Amy makes a terrifying discovery.
Vigil is forced into lockdown as disaster strikes. With communication lost, Kirsten desperately hunts for clues to the source of the threat to Vigil.
Amy is trapped and running out of time. Vigil’s crew must identify the traitor or risk tragedy.