The film opens in Kandahar Province, Afghanistan at night where Johnny Talbot, the son of American Embassy superior Bill Talbot (Robert Forster), is in an operation against the Taliban. However, the helicopter carrying Johnny and Ray is hit by a missile. Immediately, the Taliban capture them both. The next morning, Johnny is burned alive.
Kate Abbott (Milla Jovovich) is an employee for the American Embassy in London, who began working in the government after most of her friends were killed in 9/11. Meanwhile, the Watchmaker named Nash (Pierce Brosnan) receives an explosive powder - hidden in a brick - using a mobile phone as a trigger, he then delivers it to the restaurant.
Kate goes to Vicker's Pharmaceutical for Dr. Perry to ask the clearance and reference of Dr. Balan but she is not allowed unless authorized by the home office. Later an embassy, inspector Paul Anderson confronts Kate for making unauthorized inquiries about Dr. Balan and agent Maureen Crane (Angela Bassett) is disappointed with her for what she did.
Kate and her four employees plan to celebrate the birthday of Bill Talbot in the restaurant, however while they head to the restaurant, Bill deletes the five visa applicants using Kate Abbott's account for what they did to his son, Johnny, in Afghanistan.
Kate and her four employees arrive at the restaurant. While Bill heads towards and Kate left the restaurant to get a last-minute present for Bill, Nash activates the bomb using his cell phone, killing all of her employees, the glassware owner - who wraps the present for him - and some passers by. Kate approaches the wreckage to see if her employees are alive. Nash approaches and is about to shoot Kate but the gas tank blows up on him - incapacitating him for a while. Kate goes on the run as Nash pursues her and he acts innocent when the police patrols and officials are in his vicinity. Therefore, the officials classify Kate as a responsible for the bombing.
Kate meets Bill Talbot at the park but he tries to kill Kate, realizing that he is being blackmailed to let certain visa applicants through after terrorists abducted his son. The two wrestle with the gun and she inadvertently shoots him. The nearby tourists film Bill - dying from his wounds - walking towards the fountain, and Kate holding his gun. Bill dies beside the fountain. Shortly, Nash arrives at the scene and Kate tries to shoot him but the gun is empty and Kate goes on the run again. Nash takes Bill Talbot's ID card - where the GPS chip is hidden in between those cards for tracking Kate's whereabouts.
Kate calls her friend, Lisa, to bring her necessities (including money) to St. Pancras train station. Dr. Balan installs a gas tank in a building for test, and using sniper rifle Nash blows the gas. The result is the destruction of many of the building's floors. This plot is to be made in New York City on New Year.
Lisa heads out to St. Pancras train station but it is being followed by Nash's men. While Nash is working on a spherical ball grenade, Kate is located on Nash's GPS and he comes for her. Kate and Lisa just met as Nash radios his men for Kate's presence. At the same time, Kate's fellow employee Sam (Dylan McDermott), along with Inspector Paul Anderson and his agents search for Kate. After Kate takes the necessities from Lisa, she makes a run for it as Nash tries to take her down again. Kate enters the train subway and Inspector Paul won't allow Sam to be with them to chase her. Kate manages to outrun the agents by entering the lower part of the subway. There, Nash finds her and throws a spherical ball grenade near her. Allowing her to escape, Kate stabs him with a metal shard.
Kate sneaks inside Bill's apartment to hide but Sam is already there. Sam believes that she didn't do anything about the attack and he tells that Watchmaker Nash is the most wanted assassin in the world. He realizes that she is being tracked and breaks her ID. Outside, Nash locates Kate is in the apartment. While Nash is heading to the room where Kate is, they find Bill's tape from Taliban containing his son's last words to him before he died. Sam calls his men but no one responds because the two in the car have been killed by Nash. Realizing Nash is in their vicinity, they manage to get out but the bomb set on the door explodes, apparently killing Sam. Kate makes her run from Nash while she is being shoot. Nash acts innocent again as the police patrols arrive at the scene.
Sally (Frances de la Tour) an embassy employee who works to track Kate after the incident - receives a call from Kate stating that she will sneak into the embassy and convinces her that she is innocent of the attack. In order for Kate to enter the embassy, Sally shuts down all the security cameras so that she will not be tracked by the agents. There, Kate accesses Dr. Balan's visa and discovers the new terrorist attack is in New York City. She manages to create a fake passport as the marines invade the embassy.
Kate arrives in New York City using the fake passport as "Amy Harrison". Twenty-eight minutes before midnight, Dr. Balan pipes the gas into the Times Square Ball. After that, Kate follows Dr. Balan to the building she hides as Nash arrives. At the rooftop of the building, Nash uses the sniper rifle to aim at the Times Square Ball, ready to blow up as the New Year starts. Along with Dr. Balan, Nash stabs him in the neck, realizing that the approximate explosion damage will not travel far. Just as Nash can pull the trigger, Kate thwarts it and a fight between the two ensues. Kate ultimately kills Nash by throwing him off the roof as the New Year starts. Shortly, the officials arrive knowing that Kate stopped the terrorist plot. Kate receives a call from Sam, who survived the injury, stating that his name was cleared.
An epilogue states that since the 9/11 attacks, the American Law Enforcement has stopped several terrorist attacks in the city alone.