In 1990s Belfast, amid the violent conflict of the Troubles, Colette McVeigh lives as a single mother in a family deeply involved with the IRA. Her life is steeped in tragedy and conflict; having lost her brother to the violence when she was a child, she is now fully entrenched in the cause. Her days are marked by secret meetings, clandestine operations, and the constant threat of capture by British security forces. This existence, while familiar, is one of perpetual tension and danger, as Colette navigates the fine line between commitment to her family and the violent demands of the IRA's mission.

Colette's already complicated life takes a dramatic turn when she is apprehended by MI5 after a botched bombing attempt in London. Facing an impossible choice between a long prison sentence, which would mean leaving her son motherless, and becoming an informant against her own, she is forcefully recruited into the shadow world of espionage. Under the oversight of Mac, an MI5 officer, Colette returns to Belfast with the mission of spying on her own kin. This precarious double life brings her into a vortex of suspicion and betrayal as she tries to protect her family while under constant surveillance from both the IRA and MI5. Her loyalties are tested to the breaking point as she wrestles with her identity, her beliefs, and the realization that her next decision could be fatal.