A central irony explored is how the perpetrator (Alistair) has spent years seeking peace and atonement, while the victim (Joe) has been trapped and "morphed" by his lifelong hatred.
The film marks the first time Northern Irish stars Liam Neeson and James Nesbitt shared the screen. Critics have praised Neeson's "stoically powerful" portrayal of a man haunted by guilt and Nesbitt's "explosive" performance as a man consumed by vengeful rage.
In Lurgan, a 17-year-old member of the Ulster Volunteer Force (UVF), Alistair Little, murders 19-year-old Catholic Jim Griffin. The act is witnessed by Jim's 11-year-old brother, Joe. This part of the film is based on a real historical event.