When Mack O'Brien left his home in Port Talbot for the seminary as a teenager, he didn't imagine he'd be back a decade later, unordained and still at a loss as to what makes for a moral life.

He takes a job as a security guard at the local steelworks and begins an uneasy transition into the world he once rejected. When the men of the steelworks organise an unprecedented strike in protest against job cuts, he sees no reason not to go along with it.

The last person Mack expects to see in the local club is Siwan Roderick - the woman who appeared out of the blue at the seminary one day to make a confession and swear him to secrecy.

Mack kept his word. But as the day of the strike nears, and as he begins to fully understand what
Siwan is planning, Mack is forced to reckon with his loyalty to her and the question of whether an act of violence can ever be justified.