Moments after discovering his daughter, Kimberly, has snuck out of the house, Jack Bauer is called into work. As head of the CIA's Los Angeles Counter Terrorist Unit office he's told that an assassination attempt will be made within the next 24 hours on the life of presidential candidate David Palmer and it's up to his team of agents to keep Palmer alive. Meanwhile, Jack's wife, Teri, sets out to find their daughter.

Convinced Jack needs to be relieved of his command, one of his team members, Tony, calls George Mason who arrives and puts the CTU under lock-down. With the help of his second-in-command, Nina, Jack slips out and heads for an address listed on the key card. Once there he encounters a shooter who hints that Kimberly's disappearance is part of a bigger plan. Meanwhile, the two boys deliver Kimberly to a man named Ira Gaines.

A man named Andre Drazen contacts Gaines. Clearly disappointed that the morning's events did not go as planned he threatens to relieve Gaines of his assignment. Across town, Jack kidnaps Cofell and, after hearing Cofell's Serbian accent, has Nina break into an old case file profiling a secret mission Jack was on in Belgrade and Kosovo two years ago. Then Jack meets Cofell's contact: the man who claimed to be Alan York.

Jack learns that one of the assassins, Alexis Mecir, is actually Victor Drazen's son and has become intimate with one of Palmer's aides. In an attempt to find the man ordering the assassinations, the aide agrees to plant a tracking device in Alexis' wallet. Back at the safe house, Teri and Kim discover their location is no longer secret or safe.

As Kim tries to get the police to call CTU, Jack discovers that the empty field where the power grid is located actually houses a secret underground government prison and that night's scheduled arrival is none other than Victor Drazen, the man Jack supposedly killed two years ago. Now Jack's convinced Victor's sons are coming to break him out.

Jack arrives at Palmer's hotel with a phone on which Drazen will call and ask Palmer to unfreeze $200,000,000 of his assets. When Palmer tells Jack that Drazen knows that's impossible, Jack grabs the phone and throws it off the balcony. It explodes seconds later. Realizing Drazen will never give up, Jack suggests having the television report that Palmer died in the explosion, leaving Jack to offer himself up in exchange for Kim.

When Jack arrives at Drazen's location, he calls and asks to speak to Kim. Andre angrily refuses and says that they known Palmer is not really dead. Stunned, Jack hangs up and immediately calls Nina to tell her there's still a traitor inside CTU. Momentarily uncertain how to proceed, Jack is suddenly shocked into action when Nina calls back with tragic news.

Palmer, Mike and Lynne discuss various ways to dispose of the ticking bomb. They conclude that the desert is the best place to set it off. Jack determines that one man must pilot the plane carrying the bomb. He chooses to fly the plane himself and bids a tearful goodbye to his daughter. Tony and Michelle become suspicious of a Middle Eastern diplomat who is asking questions about the evidence against Syed Ali. Palmer departs for Los Angeles so he can be on hand when news of the nuclear bomb reaches the public.

Palmer's cabinet invokes the 25th Amendment in an attempt to remove him from power. They place him on trial for his extreme actions during the nuclear bomb threat. Jack and Michelle work against the clock to prove that the evidence against the Middle East is false.

Ramon holds Jack hostage as he flies to Mexico. Ramon plans to kill Jack, but Jack manages to hold him at bay until the plane lands. Ramon then learns that Jack and Hector are working together to break him out of prison.

Gael is captured while trying to escape from CTU. Chappelle interrogates Gael but is interrupted by Tony, who claims that Gael is part of a bigger plan.

Anne is given a chance to clear Palmer's name, while Chase heads for Mexico to rescue Jack.

Palmer and Chappelle view a message from Jack, explaining his undercover work with the Salazars. Meanwhile, Hector tries to convince Ramon that they should deal with Bauer so that they can get their hands on the virus.

Jack has a private moment with Claudia and she blasts him for leaving her behind when he arrested Ramon.

Chase arrives in Mexico, but is captured by Hector's men. Ramon devises a way for Jack to prove his loyalty to them.

Anne manages to clear Palmer's name, but she breaks off her relationship with him.

Things finally come to an explosive head as Jack, Ramon, Nina and Chase all close in on the virus. But the deal takes an unexpected turn when Amador pulls a fast switch.

Kim becomes suspicious of Chloe when her story about her baby doesn't check out.

Sherry finds a witness who can damage Milliken, but her advantage is short-lived.

Chappelle threatens to pull Jack from the investigation for killing a material witness, but Jack persuades him to hold off when they find a fresh lead on Amador's whereabouts.

Amador and Alvers meet with the man who is planning to unleash the virus in LA within the hour.

Michelle and Gael locate the target area, but things really hit the fan when they attempt to capture Alvers in the process of releasing the virus.

Wayne argues with Sherry over the consequences of Milliken's death as the police turn up the heat on Julia.

Saunders begins making demands on the President. He forces Palmer to hold a strange press conference and then orders the death of the CTU agent who can trace him.

Jack learns of a woman who can lead him to Saunders, but a surprise attack shifts the balance of power.

As Gael's symptoms get worse, Michelle devises a way to relieve the suffering of the victims at the hotel.

Jack pushes the envelope in an attempt to force Saunders to disclose the location of the missing vials.

Sherry meets with David to discuss her terms, while Wayne breaks into her home to find the incriminating evidence.

Tony finds himself facing a harsh penalty because of his efforts to save Michelle.

As the missile speeds toward its destination, Mandy cuts a deal with Jack and the President to give up Marwan's location in exchange for a full pardon on all of her crimes.

Tony and Michelle share a happy reunion, but Jack finds his relationship with Audrey shattered as she makes her feelings known.

Logan's advisor suggests a drastic course of action when the Chinese government demands that Jack be handed over to them for trial. Palmer tries desperately to warn Jack of the danger against him.

Jack's life changes forever as Tony, Michelle and Chloe help him to evade the trap set for him by Secret Service.

Jack poses as Rossler and manages to trace one of the canisters of nerve gas, but he goes against orders from the president when the terrorists target a shopping mall.

Logan and Martha quarrel when she learns of her husband's intention to cover up the real reason for Walt's suicide.

Jack takes his fight directly to the President as he attempts to force a confession from him that will prove his involvement in the day's events. Martha vents her hatred for her husband in front of the press as Logan gives a eulogy over Palmer's body. Jack and Audrey share a tender moment when it seems the crisis has subsided, but Jack finds that his problems have only begun as his past catches up with him.

While Jack has problems with Curtis, CTU discovers a nuclear threat and raids a terrorist warehouse, and a shocking explosion shakes LA.

Jack baits Fayed with Gredenko, while the President faces a challenge to his office.

Jack rushes toward his nephew and his oldest antagonist, as a Chinese sub and F-18s race for the same destination. Chloe faints. Can Jack find any peace?

As the country reels from the recent terror attacks and faces the mounting global ramifications, the administration refuses to acquiesce and presses on with their disapproval of the Juma regime. As Jack Bauer and team head to the White House for a pivotal meeting with President Taylor, Dubaku raises the stakes when he threatens the First Family

Jack and Chloe are on the trail of a hacker who might lead them to whoever is behind an assassination attempt on President Heller... but Kate is hot on Jack's trail.

Jack Bauer and President Heller endure the unthinkable to thwart the terror attacks of mastermind Margot Al-Harazi. Meanwhile, CIA agent Jordan Reed faces a life-or-death struggle and Kate takes drastic measures to track down Margot before it's too late.

Audrey pursues diplomatic channels to try to prevent a full-scale war. Meanwhile, Jack Bauer leads Kate Morgan and Mark Boudreau on a mission to locate their target before it's too late and the world is changed forever.