When a car belonging to a known crime associate is pulled from the sea in Northern Ireland, Detective Tom Brannick finds an ominous postcard that connects to a shadowy case from the past: an assassin nicknamed Goliath. Tom and his colleague DS Niamh McGovern investigate, but the community’s distrust of the police hinders their progress.

Tom’s superior is arrested and interviewed, but Tori worries there’s not enough evidence for a conviction. Niamh remains unconvinced that they’ve finally caught Goliath and starts her own investigation.

DCI Tom Brannick and his partner, DS Niamh McGovern, are called to the scene of a shooting on the shores of Strangford Lough. Tom recognizes the victim as a wealthy accountant from his troubled past, and the subsequent investigation of the dead man’s widow, Olivia Foyle, leads Tom into a web of intrigue that is inextricably bound to his previous misdeeds.