No sooner has Jack Bauer finished a game of chess with his daughter, Kimberly, on the morning of the presidential primary, when Kimberly sneaks out of the house and Jack, who heads up the government's Counter Terrorist Unit, is called to work urgently.
On the day of the California Presidential Primary, between midnight and 1:00 AM, the spy Victor Rovner sends a message from Kuala Lumpur to USA. Meanwhile, in Los Angeles, the Federal Agent Jack Bauer has returned to his family and is having trouble at home with his teenage daughter Kimberly, who blames her mother Teri for putting Jack out of the house. Teri and Jack decide to have a serious conversation with Kim, and they discover that the girl has run away home. While trying to solve his domestic problem, Jack is called to his Counter Terrorist Unit by his colleague Nina Myers for a meeting with their chief Richard Walsh, who discloses a menace against the life of Senator David Palmer, who is running for president, and they need to find the shooter. Later, Walsh has a private conversation with Jack and tells that there is a conspiracy in the agency against David Palmer, and assigns Jack to find the conspirators. When an airplane explodes over the Mojave Desert, Jack has one additional issue to worry about.
After a 747 explodes over the Mohave Desert, Jack investigates while he continues to search for Senator David Palmer's potential assassin and the whereabouts of his daughter.
Kimberly and Janet find themselves in great danger and must look for an escape route. Meanwhile, Palmer attends a secret meeting, and Jack discovers a key card that could lead him to the terrorist organization.
Jack's suspicion that someone at CTU may be involved in the assassination attempt on David Palmer causes friction with one of his closest supporters. Meanwhile, Palmer ignores the advice of his security team to move ahead with a public appearance.
Following the shootout, Jack goes to the police station to try to get key information from Greg Penticoff. Meanwhile, Kimberly gets handed over to Gaines and Palmer arranges a meeting with reporter Maureen Kingsley.
Jack's wall that separates his work and family comes crumbling down when he discovers Kimberly may have been kidnapped. Meanwhile, Palmer discovers his family has been protecting him from a secret that could hurt his campaign.
Jack returns to CTU in an effort to keep his wife and daughter alive. Meanwhile, Palmer tries to convince his son that they need to tell their side of the family tragedy.
As the California primary officially begins, Senator Palmer wants to rewrite his campaign speech so that the truth of his family tragedy can be revealed. Meanwhile, Jack tries to find the assassin and keep his wife and daughter alive.
Jack's efforts to save Senator Palmer backfire, turning Jack into the primary suspect. Meanwhile, Teri and Kimberly band together at the compound to help each other cope with being hostages.
Jack, now a wanted man, evades police while working with CTU to find Teri and Kimberly. Meanwhile, Tony and Nina track down information about Gaines as a new Director of CTU takes the helm.
Jack goes on the offensive and takes a colleague of Gaines for a wild ride in a limousine to find clues about his wife and daughter's whereabouts.
Jack begins closing in on the location where Teri and Kimberly are being held hostage. Meanwhile, Teri and Kimberly create a shock of their own as things get violent at the compound.
Gaines' boss finally loses patience with Gaines' ineffective pursuit of Jack, as Jack turns the tables. Meanwhile, Nina and Tony learn the plot to assassinate Senator Palmer goes deeper than they thought.
CTU discovers that a backup plan is under way to assassinate Senator Palmer. There are more foreign shooters hired and they may already be in the country.
Senator Palmer insists on speaking to Jack face to face despite CTU bureaucratic red tape. Meanwhile, Teri and Kimberly are taken to a safe house guarded by CTU agents.
Jack makes contact with an agent in New Orleans who may have information concerning the assassination conspiracy. Meanwhile, Nina debriefs Teri and tries to get all information that may help with the investigation.
Jack brings in someone from Senator Palmer's staff to help him arrest one of the would-be assassins still out to kill Palmer. Meanwhile, Keith does some of his own investigative work to find out what really happened in the death of Dr. Ferragamo.
While Jack tries to turn up the heat on the remaining shooters, he is forced to work with an overzealous CTU agent. Meanwhile, Senator Palmer must decide what to do with the key evidence Keith obtained about Dr. Ferragamo's murder.
Following the murder of the agent in New Orleans, Jack learns of a location in Saugus that could hold the key to the entire assassination and kidnapping plot. Meanwhile, Kim finds her way back to Rick, who is in some trouble of his own.
Dennis Hopper makes his first appearance as a Balkan war criminal who blames Jack for the death of his loved ones. His attempt at revenge is the motive behind the conspiracy.
Jack is at the mercy of the criminal masterminds he has been working all day to capture, while Kim must prove her innocence after she is mistakenly swept up in a police drug sting.
Victor and Andre Drazen use Jack as trade bait to get Alexis Drazen back. Meanwhile, Kimberly is again put in harm's way.
"The mole" within CTU is finally revealed. Meanwhile, the Drazens use Kimberly to make Jack do their dirty work.
The action-packed and suspenseful season finale finds Jack in the ultimate showdown with the Drazens. Meanwhile, "the mole" causes more damage than anyone could have anticipated.