In the scorching deserts of Jordan, IDC agent Sean Wong (Andy On) and his dedicated team embark on a dangerous mission to safely escort Kenner Osama Muhammad, a scientist who possesses a stolen copy of the smallpox virus, to Norway. However, their journey quickly takes a tragic turn when their convoy is ambushed by a ferocious group of attackers. Amidst the chaos, Sean's true nature is unveiled as he betrays his teammates, Jon Man (Jay Chou) and his girlfriend Ice (Michelle Bai), leaving them to face grave consequences. This betrayal leads to a heart-wrenching outcome: Ice suffers a fatal injury while Jon is left with a bullet lodged in his brain, his remaining time rapidly diminishing.
Fast forward three months, and the world is shaken by reports of a devastating outbreak aboard a Malaysian freight ship, with crew members succumbing to the smallpox virus. Kenner’s fate takes a dark turn when he meets a grim end under the wheels of a passing truck, forcing Sean to recalibrate his plans. He sets his sights on an arms dealer named Tyler (Jared Robinson), devising a diabolical scheme: to mutate the virus into a biological weapon, concoct a vaccine, and sell it to a morally corrupt pharmaceutical company.
Meanwhile, in Beijing, Jon Man's life takes a melancholic shift as he returns to his mother, Elaine (Elaine Jin), to spend what might be his last days with her. During this poignant reunion, she reveals a long-hidden family secret: Jon has an estranged brother, Man Yeung (Nicholas Tse), abandoned by their father, Man Tin (Liu Kai Chi) during their childhood. This revelation weighs heavily on Jon, prompting him to confront not only his mortality but the essence of his very identity.
Things intensify in Kuala Lumpur's Malaysian court, where Man Yeung faces a daunting set of charges due to his past misdeeds. In a bold twist, he orchestrates a cunning escape while being led to prison, thanks in part to the assistance of the unscrupulous police officer, Russell (Philip Keung).
Onboard a flight to Malaysia, Jon crosses paths with Dr. Rachel Kan (Lin Peng), a talented physician associated with the Asian Centre for Disease Control and Prevention (ACDC). Unbeknownst to Jon, Rachel's abduction by Yeung upon their arrival initiates a chain of events that alters both of their lives dramatically. Growing suspicious, Jon follows the vehicle containing Rachel's captors, finding himself unwillingly pulled into a violent confrontation with Yeung and his gang. Although a crash allows Yeung to escape, Jon is left shaken and unaware of his connection to the adversary.
Back in Malaysia, Jon receives a shock during a fateful reunion with his father and Yeung's daughter, Cheung-sing, who reveals that Yeung is indeed his long-lost brother. Amidst escalating chaos, Yeung and his men launch an audacious raid on Rachel's residence, taking her mother hostage and compelling her to obtain a sample of the lethal Carnot virus from ACDC.
The next day, as Yeung and Rachel escape with the precious virus, chaos reigns on the streets of Kuala Lumpur, culminating in a frantic chase that results in tragic losses, including innocent lives and Yeung's own associates. In a tense showdown, Rachel is recaptured by Mark (Sammy Hung), a ruthless henchman aligned with Russell. As Yeung manages to flee, pursued by Russell and his corrupt allies desperately seeking to silence him, he makes a desperate call to his father, insisting that Cheung-sing be brought to the train station.
Coincidentally, Jon finds himself in the area, intending to reunite with Rachel, but instead witnesses the unfolding drama. He teams up with Yeung to face off against Russell's thugs, leading to a confrontation that exposes their brotherly bond, shocking Russell into a frenzy of violence. In a climactic battle, countless truths unravel as Jon and Yeung engage in a stark struggle, only to be interrupted by Russell and his men at the train depot, where Jon’s father sacrifices himself to ensure their escape.
Russell’s ongoing manipulation reveals the shocking reality of Jon and Yeung's brotherhood, prompting him to order Jon's elimination while he seeks refuge in a hospital. Meanwhile, Yeung confronts Russell in a nightclub, extracting a brutal price for his daughter’s release. A fateful accident occurs as Russell meets his end on the street—a cruel twist of fate in the tumultuous pursuit.
The following morning, in a chilling exchange, Yeung delivers the Carnot virus sample to Sean in return for his daughter's safety. However, Rachel faces coercion as she is forced to merge the virus with the smallpox, setting the stage for terrifying consequences. Jon's timely intervention disrupts Sean's sinister plans as he asserts control, leading to a desperate showdown.
As chaos ensues around them, Jon and Yeung become allies, blending their resolve to overcome the tumultuous storm that has risen against them. Each passing moment escalates tension as Jon wrestles with his fate, navigating obstacles to finally achieve a confrontation with Sean, leading to a sacrificial climax where Jon enables Yeung to take the final shot that ends Sean’s reign of terror.
In the aftermath of this violent turmoil, Yeung turns to the IDC authorities, taking Cheung-sing to Beijing for a profoundly emotional visit with her mother, signifying his journey toward forgiveness. As the credits draw near, Jon’s reflective voiceover resonates with a poignant proclamation that family is everything—yet the uncertain fate of those he loves lingers in the air, leaving viewers on the edge of their seats.
