Season 1 of Vigil is about on board a nuclear submarine. When a crew member is discovered lifeless on board the Trident HMS Vigil, police in Scotland are referred to as in to analyze. The catch? The UK’s nuclear deterrent should stay unbroken, so the submarine stays on patrol and Detective Chief Inspector Amy Silva (Suranne Jones) should go aboard to start an investigation. Though the dying was written off as an unintentional overdose, Amy suspects foul play. However when the crew closes ranks within the face of Amy’s questioning, a brand new menace overshadows her inquiry.