Former garda Jack Taylor investigates the disappearance of a woman's teenage daughter, a task that leads him into the underworld of Galway City. When four bodies turn up in the river and Jack's favourite barman dies in mysterious circumstances, everything he believes in begins to unravel - making him question those closest to him.

Jack is returning to his beloved Galway clean and sober after having been away for a year. It is not long before Jack is dragged back under when he uncovers a group of vigilantes calling themselves The Pikemen, after old Irish Freedom Fighters. Jack is pushed to the brink like never before. He soon realizes that the only way to see justice done is to do the very thing he has been trying to avoid: to become like the Pikemen.

Jack is hired by the daughter of a former inmate of the infamous Magdalen Laundries, a home for wayward girls, to find the identity of a former nun, known only as Lucifer. The seemingly simple case grows complicated when two young boys are murdered. Jack sets out on the old nun´s trail, uncovering religious hypocrisy and abuse.