Teri receives a phone call from Alan York who says his daughter, Janet, is a friend of Kimberly's and is also missing, so the two parents join forces to try and find the girls. Even as Jack is secretly called out of the office and given an encrypted key card containing information on the Palmer hit that could lead him to a dirty agent within his organization, the explosion of a 747 over the Mojave Desert becomes yet another piece in the puzzle.

Kimberly and Janet realize they are in danger after it becomes clear that their two dates have kidnapped them. Despite the threat on his life, Senator Palmer sneaks out of his hotel to meet a reporter who has damaging information that could affect his campaign. Back at the office, Jack has Jamey, a member of his team, decrypt the key card.

In order to save his wife and daughter, Jack is ordered to deliver a briefcase to a man at Senator Palmer's rally. Realizing this man must be the assassin, Jack struggles to find a way to protect both Palmer and his family. Back at the CTU, Nina and Tony think they have found the traitor within the midst.

While Jack is questioned at the CTU, Teri and Kim are taken to the clinic to be examined. Meanwhile, certain he recognizes the name Jack Bauer, Palmer has Jack's background investigated. When he discovers that Jack was the sole survivor of a secret mission that he authorized two years ago, Palmer becomes convinced Jack is out for revenge and insists on talking to Jack face to face.

Alexis' contact turns out to be a power company worker who was being paid to shut off the electricity to a power grid out in the middle of an empty field. As Jack and Mason follow up on that lead, Kim's search for information lands her in jail, even as Palmer's press conference disclosure could ultimately put his own son in jail.

Jack's fears are proven true when Andre Drazen breaks into the underground facility to rescue his father. With Jack as his prisoner Victor calls CTU, but Mason tells him he doesn't negotiate with terrorists. Desperate to buy some time, Jack tells Victor that his son, Alexis, is still alive. Back at the police station the police finally let Kim go, but her drive to CTU doesn't go as planned.

Jack has Nina connect Victor Drazen to a hospital phone so he can talk directly to Alexis. Nina then advises Palmer of the situation. Palmer urges Mason to arrange the exchange Drazen proposed: the return of Jack for the return of Alexis. Although Alexis is delivered, Drazen holds onto Kim and tells Jack he needs to do one last thing if he wants to see his daughter again.

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.

It's been a year since Jack lost his wife, and the emotional toll includes estrangement from his daughter Kim, who is now a live-in au pair for a troubled family. Jack is no longer with CTU, and no longer interested in that line of work - until he's summoned directly by President Palmer. The situation: terrorists have planted a nuclear device somewhere in Los Angeles and plan to detonate it within 24 hours.

Jack reestablishes his undercover identity to join a crew of suspected terrorists that may know something about the nuclear device planted in Los Angeles. Posing as career criminal Jack Roush, his only hope in proving his loyalty to them lies in the package he's carrying. Meanwhile, President Palmer deals with a curious press, including one particularly skeptical reporter; Kim tries to protect Megan from her father; and Kate Warner follows up on suspicions about her sister's fiancé.

Kim and Miguel are arrested and the police plan to take them back to LA. Tony questions Bob Warner at CTU and learns more about his government connections. Palmer discovers a traitor in his ranks when the journalist whom he was holding is set free. Nina pulls a deadly countermove, setting herself up as the main player in the search to locate the bomb.

Jack and Kate try to break Marie's resolve so they can learn the location of the bomb. Palmer confronts his ex wife with the information that Stanton gave them. George finally steps down as director of CTU and hands the position over to Tony. Kim discovers her host's deception.

Jack, Kate and Wallace fight to escape from a deadly band of commandos. Palmer decides to take a stronger stance against the civil unrest resulting from the bomb explosion. Tony's trust in Michelle is broken when he suspects her of betraying him. Kim's worries seem to be over when she learns the charges against her have been dropped.

Three years have passed since the events of Day Two. A van deposits a dead body outside the LA Health Unit. The body is infected with a deadly virus. Tony, now in charge of CTU, learns that this is a blackmail tactic to get the US government to release a drug lord, Ramon Salazar, whom Jack has just brought down, before Salazar's brother releases the virus into LA.

Jack and his new partner, Chase Edmunds, prepare to sign a deal with Salazar at the prison. Salazar delivers a mysterious warning to Jack before killing his lawyer.

Palmer is alive and well, and has returned to LA for the first time since the attack three years ago. He is running for re-election and is preparing for an important debate with a rival senator. He is accompanied by his brother, who happens to be his chief of staff and his doctor, who also happens to be his girlfriend.

A young boy, Kyle Singer, is seen examining a large, mysterious bag of white powder. He plans to deliver it to some dealers later that day, but he is being watched by Salazar's men.

Kim now works at CTU and has been dating Chase for three months. Kim wants to tell her father, but Jack has a mysterious health problem that may make things more complicated.

Jack and Chase quarrel over Chase's relationship with Kim. Meanwhile, they learn of a lead to the possible whereabouts of the virus after raiding a crack-house.

Linda breaks up with Kyle when she learns that he is planning to make a drug delivery.

Wayne approaches Palmer with information about his girlfriend that could damage his chances for re-election, while a CTU employee is not what he seems.

Claudia manages to free Chase from his captors, but she pays a high price for her efforts.

Wayne turns to Julia, while Palmer calls on Sherry for help against Milliken.

Jack and Ramon make plans to get to Nina, in the hopes of intercepting the virus.

Chloe's work at CTU is disrupted when she is forced to take care of her baby.

Jack forces Nina to work with him to get the virus from Amador.

Palmer meets with Sherry and convinces her to help him deal with Milliken.

Chase remains in Mexico to help with the capture of the virus.

Ramon and Hector quarrel when Hector wants to pull out of the deal.

Jack and Chase interrogate Nina, but the worm turns when she causes havoc with the CTU computer systems.

Chappelle puts Chloe under guard when she refuses to answer questions about the baby, but is forced to release her when she is the only one who can deal with the crisis.

Sherry takes her battle directly to Alan, forcing Julia to act as her accomplice.

Jack attempts to use Saunders' daughter as leverage to gain control of the virus, while Palmer must deal with the discontented press.

Michelle gets the results of her test, while Adam finds that the virus has struck too close to home.

Tony finds himself compromised when Saunders exploits his only weakness.

Tony works to free Jane from CTU before Saunders can harm Michelle, but Chloe and Jack become suspicious of his activities.

Sherry meets with Palmer's political rival and proposes a deal to blackmail him.

Jack and Chase must make a powerful sacrifice when dealing with the virus.

Tony is able to help Jack one last time before he is taken into custody, while an angry victim seeks vengeance on Saunders.

Palmer makes a surprising career choice in the wake of Sherry's death.

Eighteen months have elapsed since the conclusion of Day 3. A commuter train bound for Los Angeles explodes. A man steals a suitcase from a passenger in the wreckage and then kills him.

Jack has been dismissed from CTU and now works for Secretary of Defense James Heller. Jack is involved with Heller's daughter, Audrey, and their relationship is growing serious. Jack is in LA for a meeting with CTU Director Erin Driscoll, who fired him a year ago, but he finds himself alienated at CTU by Driscoll and the new staff when reports of a possible terrorist strike come in.

A young computer hacker named Andrew Paige sees something that he shouldn't on the Internet. Suddenly, he finds himself running for his life as he is pursued by terrorists. Luckily, he is able to warn Chloe O'Brian before its too late.

The Turkish Araz family are not what they seem and it becomes clear that they are heavily involved with the day's events. Meanwhile, Heller has a confrontation with his estranged son.

Jack finds that Chloe is his only ally as he tries to prove that the train explosion is merely a diversionary target.

Jack takes Audrey to ID the man she recognized at the compound, but the terrorists get there soon after and pin them down. Jack must call on an old friend to help him escape.

Heller puts Edgar in charge of dealing with the nuclear override, while Driscoll's daughter takes a turn for the worse.

Dina is wounded when she helps Behrooz flee from Navi. Navi's boss orders him to kill his wife and son before the day is over.

Jack and Curtis finally learn the location of the override device. They try to trap the architect of the terrorist strike before the remaining nuclear plants go critical.

Tony pushes Dina to reveal more of her knowledge of Marwan, while Driscoll faces another personal crisis with her daughter.

Marwan decides to trade Jack for Behrooz in hopes of distracting CTU from his real objective.

Tony and Michelle weigh the consequences of the trade, while Curtis reluctantly interrogates Behrooz in order to learn more about Marwan.

Curtis brings in a suspect who has critical information about Marwan's next strike. Michelle orders Curtis to use harsh methods to interrogate the suspect, but things get complicated when Marwan sends a lawyer to defend his rights.

Logan's advisors begin to worry as he continues to exhibit fear in the face of the ongoing terrorist threat.

CTU scrambles to forge an alibi when a Chinese representative produces evidence of American involvement in the raid on their embassy.

Audrey gives Jack the cold shoulder, while Palmer and Logan clash over the consequences of Palmer's decisions.

Jack and Curtis close in on Marwan as the countdown for the missile launch moves ahead.

Jack is captured by the terrorists, who use Derek as leverage to force him to compromise CTU's assault operation. Logan refuses to give into the terrorist demands as the time of the co-signing of the treaty draws near. Martha tries to tell her husband of the evidence she uncovered about her phone call with Palmer, but Walt interferes with her efforts. A new representative from District arrives at CTU and begins to undermine Buchanan's authority.

Jack returns to CTU and has an emotional reunion with Audrey, while Curtis tracks the Russians and the stolen nerve gas.

Walt sends in a hit man to silence Jack.

Chloe discovers that Spencer has his own agenda at CTU.

Walt convinces Logan to have Martha institutionalized when she tells them of the attack on her.

Logan wrestles with his conscience when he learns that Martha is riding in the motorcade with the Suvarovs.

Audrey convinces Curtis to take action as Lynn continues to abuse his authority.

Jack learns that an ex CTU agent, Christopher Henderson, works for a company which is connected with the nerve gas.

Jack and Lynn must take action when they discover that the nerve gas is breaking through the protective seals that are keeping the CTU survivors alive.

Chloe wrestles with her grief over Edgar's death, while Tony contemplates revenge against Henderson.

Martha bolster's Logan's spirit as he wavers under more political pressure from Gardner.

After stowing away aboard the flight containing Henderson's contact and the incriminating recording, Jack finds himself having to deal with a pilot who refuses to cooperate.

Martha begins to break down, and Mike becomes suspicious of what she is hiding from him, while Logan tries to calm his financial backers.

Four more "suitcase nukes" are out there, and Jack's only lead takes him to the home of his brother.

Jack finds himself confronting his father while the lead terrorist needs help if he's to explode the remaining bombs.

The search for Gredenko finds Jack hunted inside the Russian Consulate and a former President calling on his ex-wife.

Jack goes rogue to save a woman, and the White House needs a fall guy for Fayed's success.

In order to prevent a war with Russia, the White House orders a trade of Jack's nephew for the circuit board, and puts Jack in custody so he cannot stop the exchange.

Following events in 24: Redemption Jack is pulled from his senate sub-committee hearing to assist with the deadly domestic threat and the investigation of former colleague Tony Almeida, his new undefined role is to help secure the nation. Meanwhile, President Allison Taylor presides over the escalating time-sensitive dilemmas linked to the unrest in Sangala. Chloe O’Brian and Bill Buchanan are on hand this season as well as FBI Agents Renee Walker, Larry Moss, Janis Gold and Sean Hillinger to cope with the unthinkable events

Since Jack Bauer has been pulled from his senate sub-committee hearing to assist with the deadly domestic threat and the investigation of former colleague Tony Almeida, his new undefined role is to help secure the nation. Meanwhile, President Allison Taylor presides over the escalating time-sensitive dilemmas linked to the unrest in Sangala. Chloe O’Brian and Bill Buchanan are on hand this season as well as FBI Agents Renee Walker, Larry Moss, Janis Gold and Sean Hillinger to cope with the unthinkable events