Season 4

Season 4 debuted in the United States with a 2-night, 4-hour premiere on Sunday and Monday, January 9 and 10, 2005 on the Fox Network.

24: Season 4 was released on DVD in North America on December 6, 2005.

Season Overview
Day 4 is set 18 months after Day 3 and sees Jack, now working for Secretary of Defense James Heller after being fired by CTU, caught up in an elaborate terrorist plot which involves both men and the daughter of Heller, Audrey Raines, who doubles as her father's chief policy assistant and Jack's lover (whilst married to another man, but separated). Jack must work with CTU and Erin Driscoll, the new Chief Director of CTU and woman who fired him, to uncover what is happening. Again, one or more moles is revealed to inhabit CTU, aiding the terrorists.

Unlike previous seasons, which focused on a singular threat and multiple enemies, this season is based around one main enemy, a Turkish terrorist named Habib Marwan who controls a series of Middle Eastern terrorist cells that launch a series of attacks against the United States.

Though much more scattered than previous seasons, this season can also be, loosely, divided into three acts:

1. A multi-layered terrorist threat is revealed in which the bombing of a commuter train is used as a diversion to kidnap the Secretary of Defense, which is used as a diversion to initiate 104 nuclear meltdowns.

2. In the second act, CTU tries to track down the architect of the days events, who starts causing distractions to sidetrack attention from the plan to bomb Air Force One.

3. In the final act the terrorists use the nuclear football to launch a nuclear warhead towards the West Coast by means of a ballistic missile.

Major subplots

 * CTU is now under the command of Erin Driscoll, the woman who fired Jack.
 * Chloe O'Brian is fired from CTU for covertly assisting Jack against Driscoll's orders.
 * Romantic tensions flare between Jack and Paul Raines, Audrey's husband.
 * The false accusation and torture of Agent Sarah Gavin.
 * After divorcing in the afterman of Day 3, Michelle and Tony come face to face for the first time in months.
 * The White House undergoes a massive change in authority, which conflicts with CTU's attempts to capture terrorists.

Main Cast

 * Kiefer Sutherland as Jack Bauer
 * Kim Raver as Audrey Heller Raines
 * William Devane as Secretary of Defense James Heller
 * Alberta Watson as Erin Driscoll
 * Lana Parrilla as Sarah Gavin
 * Roger Cross as Curtis Manning