In 1992 Belfast, Northern Ireland, the haunting shadows of Frankie McGuire's past resurface with alarming intensity. When he was just eight years old, he witnessed the brutal murder of his father at the hands of the authorities, believed to be due to suspicions tied to the Irish Republican Army (IRA). This traumatic event left an undying imprint on Frankie's psyche, molding him into the determined man he is today.
As the story shifts to the present, Frankie finds himself amidst chaos alongside three fellow IRA members, including Sean Phelan, as they are ambushed by agents from the British Army and the Special Reconnaissance Unit. In the ensuing turmoil, two of their comrades are ruthlessly killed, yet Frankie and Sean manage to escape by the skin of their teeth. With a British Army helicopter hot on their trail, Frankie's commander, Martin MacDuff, boldly asserts that the IRA must acquire Stinger missiles to retaliate.
Assuming the alias "Rory Devaney," Frankie embarks on a mission to New York City to secure these coveted weapons. With the aid of Judge Peter Fitzsimmons, an American who has long supported the IRA, Frankie is offered refuge with Irish-American NYPD Sergeant Tom O'Meara and his family on Staten Island. Unbeknownst to Tom, he is welcoming an IRA operative disguised as a mere immigrant construction worker.
Back in Belfast, Sean reunites with Frankie and procures an old fishing boat, planning to use it for smuggling the missiles back to Ireland. As Frankie enters into negotiations with black market arms dealer Billy Burke, who has his own connections with the Irish mob, he commits to picking up the missiles in a few weeks. Fitzsimmons arranges for Megan Doherty, another IRA operative posing as the O'Meara’s nanny, to deliver the funds for this perilous transaction, which Frankie stashes away in the O'Meara's basement.
As tensions rise and the stakes become more precarious, Tom wrestles with guilt over a decision to retire following a cover-up involving his partner, Eddie Diaz, who fatally shot an unarmed thief. While confiding in Sheila about his choice, their home is suddenly invaded by masked assailants. Frankie springs into action, aiding Tom against the attackers while Sheila alerts the authorities, momentarily holding the intruders at bay.
After the dust settles, Frankie confronts Burke for an attempted heist on his funds, taking down one of Burke's men in the process. However, Burke makes a chilling revelation: he has captured Sean and demands a hefty ransom for the missiles. Tension builds as it becomes clear that the intruders had been searching Frankie's basement room, where Tom accidentally stumbled upon a duffel bag filled with cash.
When Tom directly questions Frankie about his identity, Frankie begrudgingly admits he is an IRA operative. Just as he attempts to reclaim the hidden money, Tom has already contacted Eddie, leading to Frankie's arrest. As he is taken away, Tom’s reality starts to unravel further, understanding that the intruders were in pursuit of something much more significant.
Amidst the escalating investigation into Eddie's actions, Tom becomes ensnared in a dark conspiracy involving both the FBI and their British counterparts. Meanwhile, Frankie clandestinely arranges a meeting with Burke in an abandoned warehouse—where Burke’s presentation of the missiles is disturbingly coupled with a grim trophy: Sean's severed head. In a moment of cunning, Frankie retaliates explosively by detonating a bag rigged for destruction, stunning Burke and his crew in a fiery retribution.
Later, as Frankie visits Megan at Fitzsimmons' residence, determination fuels his desire to see his mission through and deliver the missiles to Ireland. Yet, Tom's unexpected appearance at a high-profile cocktail event complicates matters further, allowing Frankie to slip away undetected. Convinced of his ability to save Frankie from impending capture, Megan unwittingly directs Tom towards the boat, igniting a series of events that will ultimately challenge their loyalties and connections.
The climactic encounter unfolds at the dock, with Tom sneaking aboard just as Frankie prepares to set sail with the missiles. A fierce confrontation ensues, and despite a dire injury and being disarmed, Tom finds himself staring down Frankie, who seems poised to deliver a fatal blow. But in this fleeting moment of connection, they both recognize their unwavering resolve—each a warrior grappling with insatiable odds, both willing to fight for their beliefs, regardless of the cost. As the boat navigates back to shore, with Tom clutching his dying friend, he reflects on the poignant irony: two soldiers entangled in a battle against the seemingly unattainable.
