The story of two sisters who grew up on the fractious Irish border. When one of them, who has been missing, finally returns home, the intense bond with her sister is re-ignited. Together they unearth their mother's past but uncovered secrets and resentments which have been buried deep, threaten to overwhelm them.

In darkest rural Ireland, ex-boxer Douglas 'Arm' Armstrong has become the feared enforcer for the drug-dealing Devers family, whilst also trying to be a good father to his autistic five-year-old son, Jack. Torn between these two families, Arm's loyalties are truly tested when he is asked to kill for the first time.