Just as President Logan is about to sign a new arms treaty with Russia, an assassin targets the only four people who know Jack Bauer is still alive… and he’s forced to return to Los Angeles.

As Chloe helps Jack sneak into Palmer's apartment to look for clues, the CTU figures out he’s still alive. Martha continues to insist that Palmer was trying to contact her about a matter of national security.

As the CTU sets up to storm the airport, the terrorists begin killing hostages. Jack scrambles to save Derek, who's been selected as the next to die. Martha searches for a transcript of Palmer's phone call.

Logan and Suvarov sign the arms treaty while Jack, held captive by the terrorists, tries to send a distress message to the CTU. Martha continues trying, unsuccessfully, to get Logan’s attention.

CTU is forced to investigate its own staff while a touching reunion between Jack and Audrey turns awkward. As the national threat level is heightened, unexpected players and ulterior motives surface and President Logan begins to break down.

When Jack Bauer comes face to face with an internal leak, frightening details about the looming terror threat are revealed. President Logan and the administration attempt to cope with the situation that has America facing a horrendous act of terror.

When Jack Bauer is realigned with the President’s plan to track the looming terror threat, he navigates CTU to a new lead. While this lead is pursued, the threat intensifies and the stakes rise.

Now that Jack Bauer has exposed and interrogated the administration’s link to the terrorists, President Logan reinstates him to CTU on a provisional basis. Meanwhile, First Lady Martha Logan grapples with the positioning that her husband and his advisors are planning to take and Jack and CTU operatives attempt to keep the military-grade nerve gas from taking innocent lives.

Although extremists tried to derail the signing of the historic arms treaty between the United States and Russia, the signing proceeded and as a result, America has inherited some of Russia's enemies. The terrorist mastermind, billionaire Vladimir Bierko, intimidates the administration while autocratic CTU leader Lynn McGill comes under fire from President Logan.

As the hostiles elevate the threat, the First Lady takes matters into her own hands. Meanwhile, Russian extremists plan an act of war that could change the world forever.

Martha struggles with her feelings after realizing Logan didn't try to save her. Jack goes to Christopher Henderson's home, looking for clues while the CTU rushes to head off a nerve-gas release at a large hospital.

As Jack reunites with Kim and questions Henderson, the Vice President seeks martial law. Lynn learns of his sister's murder, and Ostroff sets off a Sentox gas canister at CTU.

When Homeland Security officials Karen Hayes and Miles Papazian arrive at CTU to clean up a worrying situation, they are met with resistance. While CTU faces its own leadership issues, the Administration must deal with the recent arrival of Vice President Hal Gardner.

With the help of international intelligence agency Interpol, CTU follows new leads to Bierko while conspiracy theorist and First Lady Martha Logan questions the administration's next defensive tactic. Now that Homeland Security officials Miles Papazian and Karen Hayes have arrived at CTU, they attempt to change operating protocol involving the operatives.

When Jack Bauer interrogates the most recent link to terrorist mastermind Bierko, shocking secrets are revealed. Meanwhile, conflict between CTU and Homeland Security officials escalates while the terrorists threaten to boost the magnitude of their attack.

Jack reinforces the importance of stopping terrorist conspirator Christopher Henderson, while the Vice President and administration attempt to realign CTU. Meanwhile, an empowered Audrey is forced to make a major decision while Wayne Palmer and Agent Pierce come together.

New discoveries regarding the day’s horrific events keep Jack Bauer away from CTU. Meanwhile, Chloe and Audrey team together to assist with field operations and the investigation takes an unexpected turn.

Although President Logan claims the country is no longer under attack, marital law is still enforced and CTU remains under intense pressure to find the remaining fugitives. Meanwhile, Jack, Audrey and Secretary of Defense James Heller reunite for a pivotal meeting.

Agent Jack Bauer's intense interrogation uncovers both new leads and incriminating evidence, but his tactics have devastating consequences. Meanwhile, problematic President Logan faces more troubling issues.

Homeland Security honchos Karen Hayes and Miles Papazian react to new developments while former CTU commander Bill Buchanan works alongside analyst Chloe O'Brian to aid Jack Bauer. As this long day enters the middle of the night, the emotions at the presidential retreat escalate to new levels for the First Lady.

As Agent Jack Bauer inches closer to bringing the culprits to justice, President Logan takes unthinkable and shocking measures to impede Jack's progress. With CTU commanders Bill Buchanan and Karen Hayes covertly working together, a counterproductive dynamic is created. Meanwhile, Vladimir Bierko reenters the picture.

Agent Bauer goes to unrelenting patriotic lengths in pursuit of the incriminating evidence against President Logan. Meanwhile, the return of Vladimir Bierko reignites the possibility of a devastating new threat.

Jack and Henderson wage an assault on the submarine as Bierko prepares to launch an attack against L.A. Chloe brings in someone from her past to aid her. Martha and Aaron enlist Mike's help in their plans to expose Logan.

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.