Detective Celcius Daly is investigating the abduction of a boy by a group of travelers already under investigation for smuggling and organized crime. As he digs into the child's background, he discovers a family secret linked to an unsolved crime during The Troubles - the disappearance of a young woman and her baby. Daly's investigation shakes loose some harrowing truths about the lawlessness of Northern Ireland's border country. Undergoing an internal investigation over his handling of the search for IRA spy Daniel Hegarty, Daly soon finds himself entangled in a vigilante mission, discovering just how far a group of outsiders will go to find their own justice.