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 sees Jack, now working for Secretary of Defense James Heller after being fired by CTU's new Director, Erin Driscoll, 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.

Timeline
Day 4 started at 7:00am PST, taking place 18 months after Day 3 and approximately 6 years after Day 1.

Format
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. In addition, this season had a much higher body count than any before it; at least one character died in every episode of the season except Day 4 6:00pm-7:00pm.

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.

2. The terrorists use an override device to initiate 104 nuclear meltdowns.

3. CTU tries to track down the architect of the days events, who is planning to bomb Air Force One and launch a warhead to the West Coast (Los Angeles) by means of a cruise 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 Audrey Raines, Paul's wife.
 * Mole Marianne Taylor.
 * After divorcing in the aftermath 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 the terrorists.

Main cast

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

Special guest stars

 * Carlos Bernard as Tony Almeida
 * and Reiko Aylesworth as Michelle Dessler

Special guest appearance

 * Dennis Haysbert as David Palmer

Main guest stars

 * Louis Lombardi as Edgar Stiles
 * Arnold Vosloo as Habib Marwan
 * Mary Lynn Rajskub as Chloe O'Brian
 * Geoff Pierson as President John Keeler
 * James Morrison as Bill Buchanan
 * Gregory Itzin as Vice President/President Charles Logan
 * Jonathan Ahdout as Behrooz Araz
 * James Frain as Paul Raines
 * Nestor Serrano as Navi Araz
 * Jude Ciccolella as Mike Novick
 * Logan Marshall-Green as Richard Heller
 * John Allen Nelson as Walt Cummings
 * Aisha Tyler as Marianne Taylor
 * Mia Kirshner as Mandy
 * Tzi Ma as Cheng Zhi
 * Glenn Morshower as Aaron Pierce
 * and Shohreh Aghdashloo as Dina Araz