In London, England, Ngoc Minh Quan (Jackie Chan), a Vietnam War veteran, is on a seemingly normal day picking up his daughter Fan (Katie Leung) from school. Their excursion takes them to a dress shop in Knightsbridge, where things quickly spiral into tragedy. As Quan struggles to park his car, a man on a motorcycle parks haphazardly between the dress shop and a neighboring bank. When Quan confronts another driver aiming to steal his parking spot, a bomb suddenly detonates, obliterating both the bank and the dress shop. The explosion claims the lives of his daughter Fan and eleven others, with many more left injured.
A news station receives a call claiming responsibility for the bombing from a group identifying themselves as the Authentic IRA. The station's head dispatches his team to uncover more information and determine if other terrorist organizations played a role. Ian Wood (Rufus Jones), a photographer, arrives at the explosion site, only to find Quan cradling Fan's lifeless body amid the wreckage.
Meanwhile, the members of the IRA monitor the emerging news from their hideout, determining to keep a low profile to avoid detection. Liam Hennessy (Pierce Brosnan), the Irish Deputy Minister, is in bed with his mistress Maggie (Charlie Murphy) when he receives a frantic call from his wife Mary (Orla Brady) regarding the explosion. Anxieties rise as Hennessy attends to various political discussions over the bombing, pushing for accountability and seeking a complete inventory of explosive caches among the groups.
Left distraught by the loss of his daughter, Quan finds himself forsaken and seeking solace in vengeance. Despite the cautions of his friend and coworker Lam ([Tao Liu]), he is resolute in pursuing the bombers. Seeking answers, he confronts Commander Bromley (Ray Fearon) at Scotland Yard to offer his life savings for information. However, Bromley denies him, insisting they currently lack the crucial details.
Determined, Quan travels to Belfast to confront Hennessy directly but is initially rebuffed. However, the strange connection between them becomes evident when Quan reveals Hennessy's past with the IRA, even showcasing a newspaper article highlighting Hennessy's pride in his affiliations. Hennessy maintains his ignorance towards the identities of the bombers, leaving Quan unsatisfied and infuriated.
In a show of desperation, Quan fashions an improvised explosive device that devastates a bathroom in Hennessy's office building. The act sends ripples of fear and urgency through Hennessy's camp. Meanwhile, Hennessy contacts his nephew Sean Morrison (Rory Fleck-Byrne) in New York, bringing him back to London to assist in identifying those responsible for the bombing.
As Quan continues his relentless pursuit, he manages to surveil Hennessy, taking incriminating pictures of him and Maggie during secretive encounters. Following a series of violent escalations, Quan ambushes Hennessy's men in his hunt for retribution. Even as Maggie creates chaos of her own, playing both sides, her loyalty to Hennessy becomes increasingly dubious.
The tension escalates to new heights when another deadly explosion rocks the city, claiming more innocent lives. Hennessy finds himself cornered, his machinations unraveling as the repercussions of his associations with Maggie and his failure to protect his family haunt him. Amid the ensuing chaos, Quan’s search leads him to discover the bombers’ hideout, where he faces off against them in a brutal showdown.
With grim determination, he extracts names and cracks the sinister network that brought about his daughter's demise. As the police close in, the layers of betrayal and connection arise leading them to Hennessy, where the truth unravels, and just revenge beckons on the horizon. In a dramatic culmination, Quan confronts Hennessy one last time, sealing their fates amidst the echoes of his lost family, forcing him to face the painful consequences of past choices.
Having exacted his revenge, Quan returns to his restaurant, where an agent vigilantly observes him under Bromley’s instruction. Yet, for now, the weight of his grief and tumultuous journey intertwines with a spark of humanity when Lam finds him, enveloping him in a moment of solace.
