25 Episodes · Premiered January 15, 2006 · Ended May 22, 2006
Is set 18 months after Season 4 ended. It begins at 7:00 a.m. Jack is believed to be dead by everyone except a few of his closest friends. He is forced to resurface when some of those friends are murdered and he is framed by terrorists with connections to the American government. The acquisition of nerve gas to protect U.S. oil interests in Asia backfires, and Jack discovers an insidious conspiracy while trying to stop those responsible.
An assassination rocks the nation as President Logan prepares to sign a treaty with the Russians that promises a new level of cooperation in the war on terror.
Jack is framed for a high-profile crime and tries to find the real culprit to clear himself.
Jack is still on the run, but he attempts to follow the leads he's discovered on a terror threat involving Russian separatists.
The terrorists acquire 20 canisters of nerve gas, and matters at CTU are further complicated when Lynn McGill (Sean Astin) from the district office arrives to oversee operations.
CTU tries to find a mole in its midst, and a suspect hiding among the hostages at the airport introduces a harrowing new element to the terrorist equation. Lynn McGill: Sean Astin.
Allegiances are tested as the line between the good guys and bad guys blurs. Lynn McGill: Sean Astin.
With 20 canisters of weaponized nerve gas in the hands of the terrorists, Jack rejoins CTU until the crisis is over.
Jack pretends to be Rossler, the programmer who was making a new arming chip for the nerve-gas canisters, in hopes of being taken to where the terrorists are, but the militants have another agenda.
McGill orders Jack back to CTU for disobeying instructions at the mall, but Jack ignores him to follow a lead on the terrorists that he received from an unlikely ally.
Following a lead on a company that made nerve gas for the military, Jack encounters an old nemesis. Meanwhile, terrorists plan an attack.
As the Russian separatists make plans to use the nerve gas on American soil, CTU races against the clock to try to thwart them. Elsewhere, Jack faces old nemesis Christopher Henderson.
Jack continues to try to get information on the location of the terrorists from Henderson.
CTU deals with the aftermath of a terrorist attack, and Jack hopes that his old nemesis Henderson will lead him to the terrorists.
Jack and Curtis run down a lead that Audrey found from decrypting Henderson's computer files; Vice President Gardner puts pressure on President Logan; and Bierko and the terrorists plan their most insidious attack yet.
CTU follows up on information received from terrorist collaborator Collette Stenger; a CTU insider becomes a suspect, and Chloe plays a key role in the investigation.
Jack fears that whatever Henderson was willing to give up his life---and his wife---to keep secret may be bigger than anyone knows, and wants to make finding Henderson priority No. 1.
Jack and Wayne Palmer go after a piece of evidence that will prove who's involved with Henderson in the terrorist conspiracy. However, martial law, Homeland Security's takeover of CTU and an all-points bulletin for Jack's arrest impede their efforts.
Jack tries to get evidence against Henderson's coconspirator to the attorney general with Henderson in pursuit.
Jack goes after Henderson, with help from Buchanan and Chloe.
Jack gets airborne in a search for crucial evidence, with help from a surprising ally on the ground.
Jack tries to stay alive, with a little help from his friends, and Audrey gets some good news.
Seemingly resolved aspects of the terrorist conspiracy and President Logan's involvement in it become unraveled, and a surprising alliance is forged.
Bierko and the terrorists have seized a submarine and threaten to use the weapons system, while unlikely allies
With the evidence against Logan destroyed, Jack comes face-to-face with the president and tries to trick him into confessing his involvement in the David Palmer assassination.
