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.
The impossible has happened: Jack is living clean and dating a mature woman – rumour suggests he is even attending mass! The accidental deaths of two students appear random, tragic events, except that in each case a copy of a book by John Millington Synge is found beneath the body. Jack begins to believe that a calculating killer is out there, enticing him to play.
The decapitation of Father Joyce in a Galway church horrifies even the most jaded citizen. Jack, devastated by a recent trauma of personal loss, has always believed himself to be beyond salvation. An eerie mix of exorcism, a predatory stalker, and an unlikely attraction conspires to lure him into a murderous web of dark conspiracies.