Sean Miller is the main antagonist in the 1987 novel Patriot Games and the 1992 film of the same name. He is an highly skilled Irish terrorist.
Sean Miller is a terrorist who participates in an attack on Lord William Holmes alongside his younger brother, Patrick, and ULA leader Kevin O'Donnell. However, he is thwarted by Jack Ryan who kills Patrick but is wounded while doing so. A shocked and distraught Miller is then arrested and put on trial, where he claims he will get back at Ryan for what he has done. While Ryan receives a knighthood for his actions, Miller is driven in a police van to Albany Prison on the Isle of Wight. However, along the way, he is freed by his associates and they kill the policemen present.
In order to take revenge on Ryan, Miller attacks Ryan's wife and daughter on a highway and cause them to crash. They survive the crash but are seriously injured. After completing various training exercises at a terrorist camp in Libya, Miller and his accomplices travel to the US to capture Lord Holmes who is visiting Ryan and his family at their house. The group of terrorists raid the house in search of Holmes, but Miller searches for Ryan instead. Ryan leads his family away from the house but the terrorists quickly follow, so Ryan takes a boat alone and drives out into the distant waters to lure them away from Holmes and his family.
Out at sea, Miller fires at Ryan, determined to avenge his brother. However, when the other terrorists realize that Holmes isn't on the boat, they try to convince Miller to turn round. Miller grows increasingly frustrated with them to the point that he guns them down before continuing his pursuit. He drives up to Ryan's boat and after failing to shoot him, he jumps into the boat himself and the pair of them fight. Miller tries to attack Ryan with an anchor but it ends up getting lodged in the boat. After being throttled with a mooring pole, Ryan catches Miller off guard and pushes him backwards onto the anchor, which impales him through the back. Miller gasps and dies soon after, and Ryan leaps off the boat just as it reaches a group of rocks and explodes.
Book vs Movie
In the movie, Miller is given a somewhat sympathetic drive behind the reason for his intense hatred of the Ryan family, with his brother dead at the hands of John Ryan. However, the book gives the reader a vastly different Sean Miller. He is a ruthless sociopath who is so devoted to his cause that he quietly sits through his own trial and coldly executes several individuals during his escape from the ferry transporting him to prison. This is a vastly different Miller from the driven and emotional man seen in the film.