On his wedding day, Niall's celebration is disrupted by an unexpected visit from Ruben, a deeply volatile figure from his past. The surprise reunion triggers chaos and immediate violence, sending the narrative back through the decades to show how their complicated, forced brotherhood first began.

In 1989, a lonely and adrift Niall struggles to adapt during his first year at university in Glasgow. Desperate to fit in, he reaches out to Ruben to join him and his flatmates for freshers' week. What begins with excitement quickly spirals out of control, concluding with devastating consequences.

In 1993, having graduated at the top of his class, Niall hopes to move to England to escape Ruben's shadow. However, his future plans are threatened when his family pressures him to lie in court about Ruben's violence. Niall faces a heavy choice as Ruben claims to have changed for the better.

In 2008, following a personal breakdown, Niall's world is entirely upended by news of Ruben's possible return. As Niall becomes dangerously consumed by Ruben's new life, a toxic obsession takes hold. Their eventual reunion erupts into a violent confrontation that forces them to face the past.

In 2010, Niall and Ava navigate major life changes together, while Ruben faces growing challenges in his own volatile relationship with Mona. Driven by tension, Niall makes an impulsive decision regarding Mona and Ruben, setting off an emotional chain reaction with serious costs for everyone.