杰克（哈里森·福特 Harrison Ford 饰）曾是中情局的一名情报员，在一次度假中，他偶然目睹了一场以北爱尔兰国务大臣霍姆斯（詹姆斯·福克斯 James Fox 饰）为目标的恐怖活动，职业习惯让他无法对此坐视不管，在杰克的协助下，恐怖份子米勒（肖恩·宾 Sean Bean 饰）被捉拿归案，杰克也得到了赢得的奖赏。 虽然行动失败了，但恐怖分子们并没就就此罢休，而是决定再干一票，此时已经越狱成功的米勒主动请缨加入行动，他的脑中只有一个念头，那就是向杰克寻仇。很快，敏感的杰克就发现自己和家人正处于极度危险之中，为了捍卫国家和平，更为了保护自己的家人，杰克回到中情局，重操旧业。
Jack Ryan (Ford) is on a "working vacation" in London with his family. He has retired from the CIA and is a Professor at the US Naval Academy. Jack gives a lecture at the Royal Naval Academy and then walks out to meet up with his wife Cathy and daughter Sally.
Meanwhile, Cathy and Sally are sightseeing near Buckingham Palace. The two come upon a British Royal Guard, and Sally tries to get the guard to react by doing an improvised tap dance in front of him. She's impressed when the guard, trained to ignore distraction, has no reaction to her antics.
As Sally and Cathy walk away from the guard, en route to rendezvous with Jack, they walk by a stolen cab, in which sit three Ulster Liberation Army (ULA) terrorists: Kevin O'Donnell, the driver, as well as Sean Miller (Sean Bean) and his younger brother Patrick. The three are loading their guns as they prepare to carry out a scheduled ambush on Lord William Holmes, British Secretary of State for Northern Ireland and a member of the British Royal Family (the cousin of the Queen Mother). As they finish loading their weapons, another terrorist, Annette, radios to them that Lord Holmes is leaving the palace with his wife and son.
As Lord Holmes's car leaves the palace, the terrorists' car falls in line behind him. They follow the car, headed for the ambush point. As they drive, O'Donnell and the Miller brothers don ski masks.
Meanwhile, Ryan is about to cross the street to meet with his wife and daughter. He arrives at the same time that Lord Holmes's car is passing through the area.
Suddenly, another cab, parked on the side of the road, driven by Annette, pulls out and swerves in front of Lord Holmes's vehicle. Simultaneously, O'Donnell's vehicle swerves to a stop behind the car. The Millers and another accomplice jump out and quickly plant a bomb underneath the chauffeured car's engine. Ryan sees what's going on and hastily gets his family to cover just as the bomb is detonated. Moments later, Sean and another accomplice begin shooting into the car, riddling Lord Holmes's driver and bodyguard with bullets. The onslaught does not kill Lord Holmes, who is currently using his body to shield his family. Sean marches over to the rear door and orders Lord Holmes out of the car at gunpoint. Ryan, unable to stand being just a bystander, immediately breaks cover, runs up behind Miller, and disarms him. As Ryan grabs Sean's pistol, he is shot in the left shoulder by another terrorist. Ryan returns fire, hitting one of the other terrorists in the shoulder. Patrick attempts to flee, but Ryan fatally shoots him in the chest. Seeing two of the royal guards racing towards the scene, the remaining terrorists quickly get back in their cars and drive off, leaving Sean to be captured when the authorities arrive. They retreat back to a warehouse, where they change out license plates.
Ryan wakes up in a hospital, recovering from the wound to his shoulder. He's visited by a representative from the US consulate and officers of the London police and questioned about his heroics. He's told about both Kevin O'Donnell, the leader of a violent ULA splinter group and Sean and Patrick Ryan, who were both orphaned at a young age and came under O'Donnell's care and tutelage. Sean is an especially dangerous and violent sociopath who shares O'Donnell's radical views about British rule of Northern Ireland.
Ryan is called to testify against Miller as a witness. Though the defense attorney questions Ryan's involvement in the incident, citing that he's not a field agent with the CIA or any other organization that would operate in his manner, Ryan holds his own. Miller has an outburst as Ryan is led out of the court chamber and vows revenge. Subsequently, Miller is convicted on all charges and sentenced to life in prison. Ryan is awarded the order of Knight Commander of the Victorian Order, and eventually returns to the United States. When they arrive, Cathy tells him she's been having morning sickness and that's she's pregnant.
