On the rural west coast of Ireland, ex-boxer Arm is the faithful right-hand-man to the drug-dealing Devers family, doling out beatings as his means of remittance. Dympna, the eldest of the Devers offspring, took Arm out of the ring and under his wing. He exploited Arm’s isolation, offering him a surrogate family, in exchange for his unwavering obedience.
Arm has since started a family of his own; he has a young autistic boy, Jack, his relationship with whom is the closest thing he has to unadulterated love. Arm struggles to acknowledge the full significance of Jack’s diagnosis, thinking that a father’s attention will cure the condition.
When our story begins, Jack’s mother Ursula has just found a school in Cork where her son can finally get the help he needs. Estranged from Arm, she intends to move there with Jack. Quietly rattled by this, Arm is then asked to kill Fannigan, a dealer who has wronged the Devers clan. Torn between the two sides of his life, he decides to prioritise Jack and spare the marked man, despite telling the Devers family that the problem has been dealt with.
Soon enough, however, the unhinged uncles of the Devers family – Paudi and Hector – uncover the truth and Arm is forced to violently confront his surrogate family, in order to set his son free.