| The mysterious disappearance of a Scottish fishing trawler and a death on-board the submarine HMS Vigil bring the police into conflict with the Navy and British security services. DCI Amy Silva and DS Kirsten Longacre lead an investigation on land and at sea into a conspiracy that goes to the very heart of Britain’s national security. |
| Name | Character | Episodes |
|---|---|---|
| Rose Leslie | DS Kirsten Longacre | 12 |
| Suranne Jones | DCI Amy Silva | 12 |
| Gary Lewis | DSU Colin Robertson | 12 |
| Dougray Scott | Marcus Grainger | 6 |
| Connor Swindells | Simon Hadlow | 6 |
| Romola Garai | Eliza Russell | 6 |
| Lauren Lyle | Jade Antoniak | 6 |
| Stephen Dillane | Shaw | 6 |
| Martin Compston | Craig Burke | 6 |
| Shaun Evans | Elliot Glover | 6 |
| Adam James | Lt Commander Mark Prentice | 6 |
| Paterson Joseph | Commander Newsome | 6 |
| Amir El-Masry | Daniel Ramsay | 6 |
| Anjli Mohindra | Tiffany Docherty | 6 |
| Chris Jenks | Callum Barker | 6 |
| Oscar Salem | Captain Sattam Abdul Kader | 6 |
| Lolita Chakrabarti | Branning | 6 |
| Jonathan Ajayi | Wes Harper | 6 |
| David Elliot | Ross Sutherland | 5 |
| Noof Ousellam | Paul Townsend | 4 |
| Steven Elder | Derek McCabe | 3 |
| Dominic Mafham | Sir Ian Downing | 2 |
| Khalid Laith | Abdulah Ghazali | 2 |
| Malek Alkoni | Faisal Ghazali | 2 |
| Alastair Mackenzie | Anthony Chapman | 1 |
| Tania Rodrigues | Emma Millington | 1 |
| Rosa Escoda | Saskia | 1 |
| Kirsty Besterman | Intelligence Officer Wright | 1 |
| Kim Allan | Paramedic Fraser | 1 |
| Martin Bell | Gunner Jansen | 1 |
| Armin Karima | Nader Waheed | 1 |
| Conor Boru | Co-Pilot Roy | 1 |
| Lee Knight | Jones | 1 |