You will not know the day, or the hour, but I am coming for you...

When DS Lucy Golden discovers an abandoned car showing signs of a recent and bloody escape, the race is on to find the injured occupant, who must be somewhere close by on the Irish island of Achill. But when an anonymous threatening note is found in a pool of blood, the search team is briefed to look for a body, rather than a survivor.

Once the victim is revealed to be a retired police officer, Lucy and her team are on edge . . . was the brutal killing an act of personal revenge? Or is the killer making a statement against the wider Gardaí?

Tensions rise as bizarre clues, conflicting witness testimony, viral videos and family feuds send Lucy and her partner Detective Dan Brown across Ireland on the hunt for a vicious murderer. They're feeling the pressure at work and at home . . . Lucy's son Luc is in a stormy relationship with a wannabe social media influencer, Dan's mother-in-law is conducting a steamy affair under his roof, and Lucy fears that a recent case that got a little too personal could be the cause of her boss DI William's noticeable coldness towards her.