Plot
Former CIA analyst Jack Ryan now teaches history at the United States Naval Academy. In London with his wife Cathy and their young daughter Sally, Ryan witnesses and intervenes in a terrorist kidnapping attempt on Lord William Holmes, the British Minister of State for Northern Ireland and a cousin to the Queen Mother. Ryan is wounded but disarms one terrorist and fatally shoots two others, then subdues Sean Miller. Among those killed is Miller's younger brother. All belong to a radical IRA splinter cell led by Kevin O'Donnell. Shortly after the incident, IRA operatives attempt and fail to assassinate O'Donnell, considering him and his followers too radical.
Miller is tried and convicted for his efforts. As he is being transported to prison, O'Donnell and his team ambush the police convoy, killing the guards and freeing Miller. Retreating to North Africa, O'Donnell plans the next attempt on Lord Holmes. Miller vows to avenge his brother's death, and O'Donnell allows him, O'Donnell's lover Annette, and several squadmates to travel to the US to assassinate Ryan. Meanwhile, British police have determined that an informant has been tipping off the terrorists and are surveilling Dennis Cooley, a book shop owner, who is an IRA operative.
Back in Maryland, Ryan is informed first that Cathy is pregnant again, and then about Miller's escape. He brushes off the bad news, figuring a wanted fugitive would not have the nerve to travel all the way to the United States. Soon after, he narrowly survives an assassination attempt by Miller's accomplices close to the Academy, while Miller simultaneously targets Cathy while she drives home, causing her car to crash, seriously injuring her and Sally.
Ryan's former CIA superior, Vice Admiral James Greer, asks Ryan to rejoin the agency to help capture the terrorists. While investigating, Ryan recalls seeing a red-headed woman during the attacks on both him and Lord Holmes. Ryan approaches Sinn Féin representative Paddy O'Neil for information. O'Neil denies IRA involvement and denounces the attacks, but refuses to betray any fellow Irishmen. Ryan threatens to sabotage O'Neil's American fundraising efforts by showing images of his hospitalized daughter to the media. O'Neil eventually relents and identifies the female accomplice as an Englishwoman, Annette. Locating her will lead to Miller. Satellite analysis indicates that Miller and O'Donnell are at a terrorist training camp in Libya, along with Annette. Having been revealed as an agent in London, Cooley flees to the training camp and entreats Miller and O'Donnell to join them, even though he has no military skills. Miller dispatches Cooley on O'Donnell's say-so in order to tie up loose ends. The Special Air Service raid the camp, killing everyone, although Miller, O'Donnell, and their cohort have already fled to America to coincide with Lord Holmes's visit there.
While Lord Holmes is at the Ryan residence to present Ryan's KCVO medal, a severe thunderstorm apparently knocks out the house's power. Ryan notices the boat-house lights are still on, and he is unable to radio any DSS agents or state troopers guarding the premises. He deduces the house's power was deliberately cut and suspects an imminent attack. Ryan realizes that Holmes's assistant, Geoffrey Watkins, is the informant and forces him to reveal information. Outside, O'Donnell, Miller, and their team have killed all of the security personnel, then infiltrate the house. After Ryan and his Naval Academy associate, Lt. Commander Robby Jackson, eliminate several terrorists, Miller pursues Ryan, accidentally killing Watkins in the process. Ryan lures O'Donnell, Miller, and Annette into pursuing him on open water in their waiting speed boats. Upon realizing it is a ruse, O'Donnell demands they return and complete their mission to abduct and ransom Holmes. Miller, crazed with revenge against Ryan, refuses, then kills O'Donnell and Annette. He leaps aboard Ryan's boat where a struggle ensues; Ryan kills Miller on an anchor and jumps overboard just before the burning boat crashes into jutting rocks and explodes. An FBI Hostage Rescue Team arrives, rescuing Ryan.
In the final scene, during breakfast, Cathy's doctor calls saying the yet-to-be born baby is healthy, but the credits roll before the audience knows whether it is a boy or girl.