As the day begins, he gets caught up in an elaborate terrorist plot which involves James Heller and his daughter Audrey Raines.

Day 4 begins with the bombing of a commuter train which (unbeknownst to CTU at the time) enables the theft of a device known as the Dobsen-type Override which could be used to take control of (and melt down) United States nuclear power plants.

With Jack Bauer working for Secretary of Defense James Heller, his job brings him to CTU as a visitor on this very day.

Believing that something terrible is about to happen, Jack begs CTU director Erin Driscoll to reinstate him and begins to interrogate a suspect.

When Jack saves a civilian programmer who discovered evidence of a cyber-attack in progress (a friend of Chloe O'Brian), he allows one of the terrorists to escape and lead him to where Raines and Heller are being held.

Even though Jack rescues them, the mass streaming of the planned execution video gives the terrorists the opportunity they need to launch an attack on the firewalls and begin using the override.

Seeking extra intelligence, Bauer and Paul Raines (Audrey's ex-husband) travel to the headquarters of the defense contractor McLennan-Forrester.

However, in an effort to cover up their complicity and erase computer records, McLennan-Forrester activates an EMP, causing a blackout over an 8-square-mile (21 km2) section of downtown Los Angeles.

In a reversal of the events of Day 1, David Palmer warns Bauer of the attempt on his life, shortly after the nuclear missile is shot out of the sky.

The episodes were originally seen by cell phone users in Europe and later in the United States as part of a Fox promotion for the show.

FOX's trailer for the fourth season of 24 begins with Jack telling Audrey that he is glad he no longer works for CTU.

The Houston Chronicle said "it grabs you and never lets go", The New York Times gave it four stars and Vogue said "the series that reinvented suspense has become an addiction".

[27] In the wake of the real-life Abu Ghraib scandal and similar allegations at other U.S. military facilities housing suspected terrorists, commentators accused the show of legitimizing the use of torture in the war on terror.

"Do I personally believe that the police or any of these other legal agencies that are working for this government should be entitled to interrogate people and do the things that I do on the show?