Stephen E. Saunders is the main antagonist in the third season of 24. He threatens the U.S. with a highly lethal Cordilla virus when he was abandoned in the enemy lines when on loan from MI6 and working with the Delta Force.
He was portrayed by Paul Blackthorne.
From his service file, Stephen Saunders was a former soldier, holding his military rank as 2nd Major in the British Army and he served in a number of assignments for British Tactical Emergency Response Team, European Battle Enforcement and United Legion Technical Team before joining the Secret Intelligence Service as a field operations agent. According to Jack Bauer and Chase Edmunds, Saunders was described as a patriot and a good soldier before Jack said that something else happened to him.
He was originally part of Jack Bauer's six-man team when British Intelligence loaned him to the U.S. federal agency Counter Terrorist Unit for a secret mission to target a Balkan war criminal named Victor Drazen in Kosovo under the name of Operation Nightfall. During the mission, he was supposedly killed in the Drazen compound explosion. He survived, but was abandoned by his American teammates of the Delta Force and captured for nearly six years before he was released by the Bosnian secret police. After the failed mission in Kosovo, he lived a civilian life in England before his wife died six months prior to the time he contacted his daughter Jane.
To obtain his revenge, Saunders planned to hold the entire U.S. mainland hostage by threatening to kill millions of people with a highly lethal biological weapon Cordilla virus. He acquired the Cordilla virus from his associate, Michael Amador, whom Jack masterminded an unsuccessful attempt to get the virus to prevent him from doing any such thing. CTU tried to track Amador, but Saunders suspected this, so he blew up Amador and one of his own men with a bomb implanted in a case that was supposedly filled with Amador's money.
Saunders had an associate, Marcus Alvers, release a vial of the virus in a hotel, killing over 700 people, and threatened David Palmer that he would release more unless he did what he told him. First, he told him to say "the sky is falling" at a press conference. When Ryan Chappelle began to run money traces, Saunders saw it necessary to eliminate him, so his next order for Palmer was to kill him. Chase Edmunds ran an unsuccessful attempt to capture Saunders, who had also expected this, and Jack was forced to kill Chappelle.
Palmer did not give in to any more of Saunders' demands, however, it was discovered that he had a daughter, Jane. Jack talked to Saunders on the phone and threatened to hurt Jane, while CTU began closing in on Saunders' real hideout. However, Saunders' men had taken Michelle Dessler hostage, and forced Tony Almeida to help him escape from CTU TAC teams.
Saunders got Tony to trade Jane for Michelle, but she ran, not wanting to go with her father's men, and Chase, along with the TAC teams, engaging Saunders' men in a shootout while Jack chased Saunders. Saunders attempted to escape in a helicopter, but a U.S. Marine fighter jet destroyed it and Saunders was captured. Saunders refused to give in the location of the other vials of the virus, until Jack threatened to send Jane into the hotel where the first vial of the virus was released.
The last vial of the virus was in possession of Arthur Rabens, whom CTU told Saunders to identify in several photos of people in a subway. As Saunders looked through the pictures, Teresa Ortega, the wife of Gael, the first victim in the hotel released by the virus, took a gun and shot Saunders as revenge for her husband's death and she was arrested by CTU security detail.