24

An attack on an L.A. commuter train is followed by a possible threat to the Internet, bringing forth a suspect who arouses suspicion of more in Jack Bauer, now working for the Secretary of Defense

Eighteen months after the conclusion of Season 3, CTU has a new leader, Erin Driscoll, a steely government agent who made firing Jack one of her first priorities. After the explosion of a commuter train, Jack, who is now working for Secretary of Defense James Heller and also is romantically involved with Heller's married daughter, Audrey Raines, suddenly finds himself heading back to CTU for a meeting with Driscoll.

Driscoll orders tough measures against Richard; Chloe's trust in Jack is tested; a personal matter distracts Curtis; Jack goes to great lengths to detain a suspect; Behrooz asks his mother for help to change his father's command.

Dina reassures Debbie and Behrooz; Kalil tries to rally his fellows against Jack, who draws a crowd; Chloe recruits more help for Jack; Heller's health comes into play.

Jack must track a new lead to Heller after the police make a crucial mistake with Kalil. Meanwhile, Omar threatens great harm to Audrey unless Heller signs the confession.

In a race against time, Jack attempts to rescue Heller and Audrey before the military bombs the terrorist compound and kills everyone inside. Meanwhile, Behrooz faces a difficult order from his father.

CTU races against time to prevent the terrorists from melting down nuclear power stations across the U.S. Meanwhile, Jack reaches out to an old friend for help; and Sarah gets suspicious about Marianne.

The president orders evacuations from six cities; a trap is set for the mole; Jack and Audrey find a surprise at Tony's; Dina and Behrooz risk a stop at a medical clinic.

Heller coordinates evacuations when a nuclear plant goes critical; Edgar asks a personal favor of Audrey; Behrooz seeks help from his uncle.

Navi prepares to defend his location; Curtis interrogates Marianne, whose information sends him into the field; Audrey meets again with her husband; Tony returns to CTU for the first time since his conviction for treason.

With Audrey present, Jack questions Paul and finds a link to Marwan; Tony turns tough when Dina pleads ignorance beyond her husband; Driscoll's daughter again proves problematic.

Marwan's alias is discovered and his immediate past suggests more trouble ahead; the makers of the override attempt to control damage---to their company.

Reinforcements are brought in to track down Jack, who recruits looting victims to help send a signal to CTU; Michelle asserts her authority, with Sarah and Tony in particular. Naji:

Jack proposes a high-risk operation that prompts Michelle to call in help; Dina makes another deal and gets to see Behrooz; an Air Force pilot is pulled into Marwan's next phase.

Anderson hits a snag at the Air Force base; Marwan offers a deal to CTU, where crucial info is lost in a battle of egos; Audrey is made aware of Jack's expendability.

A Marwan operative alludes to another attack within the hour, while another gets help from Jack in searching for a missing hard drive; the president prepares to address the nation.

Two campers are engaged in Marwan's battle when they retrieve something from Air Force One; an aide notes a lack of confidence in the vice president; Tony and Michelle make peace.

A terrorist's carelessness enables CTU to pick up his trail; the new president takes cover before addressing the nation; Marwan plays the law to his advantage.

Audrey is among those chiding Jack for his treatment of Prado; Marwan tapes a message for the U.S. populace; former president Palmer is asked for counsel when Logan questions his own capabilities.

The slow pace of diplomacy prompts Palmer to approve a covert operation; Audrey makes a decision about Paul.