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.

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.

Although he prevents Palmer's assassination, Jack is taken into custody where his story of his kidnapped wife and daughter is not believed. Knowing his family will only be kept alive if he is free to help Gaines, Jack knows he must escape. Back at Gaines' compound, Teri and Kimberly struggle to stay alive, while at CTU the traitor reveals that the whole unit has been wired so Gaines can watch their every move.

While Green pressures Nina and Tony to reveal Jack's whereabouts, York leads Jack to Gaines' compound where Jack attempts to rescue Teri and Kim without backup from CTU. Meanwhile, Senator Palmer's plan to prevent a murder fails and he begins to suspect his wife may have a hand in the conspiracy.

Jack confronts Gaines who, realizing he has failed Drazen's assignment, chooses death over helping Jack. Back at CTU, Nina and Tony interrogate the mother of the traitor and learn of a secret bank account containing deposits from Belgrade. They also learn that additional assassins may be making their way to Los Angeles.

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.

During their escape from the safe house Teri and Kim become separated, and the traumatic events of the day result in Teri passing out and then awakening with amnesia. Assuming her mother has been re-kidnapped, Kim conducts her own search for information concerning her mother's abductors. When the plan to track Alexis backfires, Jack pretends to be Alexis in order to keep a rendezvous with one of Alexis' contacts.

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'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.

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.