Although fired from CTU, Jack Bauer is thrust back into action after a deadly terrorist strike and the kidnapping of his new boss, the U.S. Secretary of Defense. But it's soon apparent that the kidnapping is part of a much larger plan.
While at a meeting at CTU, ex-agent Jack Bauer tries to stop a second terrorist attack after learning the terrorists? next target is his new boss, U.S. Secretary of Defense James Heller.
Jack tracks down Chloe?s friend Andrew who discovered a dangerous virus code on the Internet, which may be connected to the attacks. The terrorists broadcast their plans to execute Heller.
Chloe secretly helps Jack, who goes to desperate lengths as he follows the terrorists hoping they will lead him to Heller.
Behrooz Araz begins to have second thoughts about his family?s part in the terrorist?s plans, and Chloe is arrested after Driscoll finds out she?s been helping Jack.
As Jack follows the terrorist, President Keller is presented with a drastic alternative even as Heller and Audrey decide to foil the terrorists? plans by taking their fate into their own hands.
Jack rescues Heller and Audrey, but soon learns that the kidnapping was just part of a larger plot, and Behrooz is shocked to discover just how angry his actions have made his father.
Edgar tries to thwart the terrorists by taking the vulnerable power plants offline, Jack and Audrey are ambushed, and Dina Araz tries to save Behrooz after he says they should go to the police.
Jack turns to the only person he can trust, ex-CTU agent Tony Almeida, as he tries to figure out which CTU employee is working with the terrorists. Edgar tells Driscoll about Marianne.
While Behrooz goes to get pain medication for his mother, Jack and Tony capture Dina and promise her that Behrooz will go free if she helps them find the override device.
Navi Araz is willing to kill his own son to see the terrorists? plan succeed, Edgar is distraught over his mother, and Audrey learns her husband is somehow connected to the terrorists.
CTU learns that a man named Marwan is behind the attacks, Audrey?s husband, Paul, agrees to help Jack, and Driscoll has to deal with her increasingly angry and unstable daughter.
As Jack and Paul get close to uncovering information about Marwan at an American company where he was employed, the company decides to protect itself by triggering an EMP device.
Jack and Paul find themselves the target of a search-and-destroy mission, Tony is stunned when Michelle shows up as Driscoll?s replacement, and Marwan launches the next phase of his plan.
Michelle calls Chloe and asks her to return to CTU, Jack and Dina?s attempt to infiltrate the terrorists cell goes awry, and Audrey realizes she still has feelings for her husband.
Fearing that information about a murdered U.S. Air Force family may arouse CTU?s suspicions,
Marwan creates a diversion by calling Michelle and offering to trade Jack for Behrooz.
CTU believes that Marwan?s plan involves a stealth fighter and their fears are confirmed when they learn Air Force One is flying in the same area as an unauthorized stealth fighter.
After Air Force One is shot down in the desert, Jack?s only hope of keeping the ?nuclear football? out of the hands of the terrorists comes from two campers who saw the plane go down.
As Vice President Logan nervously steps into the presidential position, Jack learns that the missing portion of the ?nuclear football? reveals the locations of nuclear warheads.
After President Logan botches up CTU?s capture of Marwan, he agrees to call in an advisor who has dealt with terrorism firsthand, and Chloe?s first field assignment almost ends in disaster.
Jack leads a raid to the Chinese Consulate to kidnap a man with information about Marwan?s plan, but the resulting shootout results in deadly repercussions for Audrey?s husband, Paul.
As CTU tries to hold off retaliation from the Chinese Consulate and President Logan braces for a political backlash, Jack and his team head to the factory where Marwan is hiding.
Unable to stop the launching of the nuclear warhead, Jack prepares to bring Marwan into CTU for questioning just as Edgar uncovers incriminating evidence against Richard Heller.
As the Chinese secretly launch their own kidnapping, Tony falls into the terrorists? hands, and any hope of shooting down the armed warhead in time grows more and more remote.
Even as Jack finds data indicating that the warhead?s target is Los Angeles, President Logan decides to prevent any political embarrassment by turning Jack over to the Chinese.