[1][2] The first series stars Suranne Jones, Rose Leslie, Shaun Evans, Paterson Joseph, Gary Lewis and Martin Compston, and is set in Scotland, primarily onboard HMS Vigil, a ballistic missile submarine of the Royal Navy.

Detective Chief Inspector Amy Silva of Police Scotland is sent to HMS Vigil, a nuclear-powered Vanguard-class ballistic missile submarine, to investigate a death on board, which takes place shortly after the mysterious disappearance of a Scottish fishing trawler.

The loss of the trawler Mhairi Finnea in the series bears similarities to the sinking of the FV Antares by Royal Navy nuclear-powered submarine HMS Trenchant in the Firth of Clyde in 1990.

Families of the Antares's crew expressed upset at scenes of the Mhairi Finnea foundering; however, the BBC denied that the drama was inspired by or based on a specific real-life event.

[3][4] When a Royal Air Force prototype combat drone is compromised and kills several soldiers during a joint demonstration in Scotland, Silva’s team are tasked with finding the perpetrator.

She travels to joint Al-Shawka Air Base in the Kingdom of Wudyan, a controversial ally in the Persian Gulf, and discovers a wider conspiracy intertwined with the current regime's collaboration with the British government and private enterprise on drone development.

[9] The first series received generally positive reviews from critics, with praise for the writing, pace, acting, visual style, set design, tone, and atmosphere, but it was criticised for the dialogue, plot, and inaccuracies.

[11] Filming for series 2 took place during spring 2023, across Scotland, in locations including Glasgow, Coatbridge, Motherwell, Cumbernauld, Luss, Lanark, Blantyre and North Ayrshire.

The critic consensus read, "Taking Vigil out of its original submarine relieves the cabin pressure but also much of the suspense, although Suranne Jones and Rose Leslie's rapport still provides intrigue.

"[51] Jack Seale of The Guardian awarded the second series four out of five, describing it as a "pacy, extremely good crime drama tackling murder on a military base" that was full of "political truth bombs".