Jack meets Teri and Alan York at the hospital where Janet has been admitted. But their reunion is cut short when Jack receives a phone call from Gaines telling him to follow his instructions if he ever wants to see his daughter again. Back at CTU, a dead body found in a car trunk is identified as that of Alan York. When Nina calls Teri and asks her to pass this information on to Jack, Teri suddenly realizes she is also in danger.

Now, under constant surveillance from Gaines, Jack goes back to CTU where Nina inadvertently gets in the way of Gains' plan. Teri tries to escape from York, but her call to CTU only brings more help for York. Meanwhile, Palmer tries to convince his family that they need to tell the press about a secret personal tragedy from their past before it's too late.

In order to save his wife and daughter, Jack is ordered to deliver a briefcase to a man at Senator Palmer's rally. Realizing this man must be the assassin, Jack struggles to find a way to protect both Palmer and his family. Back at the CTU, Nina and Tony think they have found the traitor within the midst.

Although he prevents Palmer's assassination, Jack is taken into custody where his story of his kidnapped wife and daughter is not believed. Knowing his family will only be kept alive if he is free to help Gaines, Jack knows he must escape. Back at Gaines' compound, Teri and Kimberly struggle to stay alive, while at CTU the traitor reveals that the whole unit has been wired so Gaines can watch their every move.

When a new boss, Alberta Green, takes over the CTU, Nina secretly continues to help Jack locate Teri and Kim while Jack tracks down investment banker Ted Cofell, a man who is mentioned on the decrypted key card. A shocked Senator Palmer learns that one of his associates may be willing to commit murder in order to protect his campaign.

While Jack is questioned at the CTU, Teri and Kim are taken to the clinic to be examined. Meanwhile, certain he recognizes the name Jack Bauer, Palmer has Jack's background investigated. When he discovers that Jack was the sole survivor of a secret mission that he authorized two years ago, Palmer becomes convinced Jack is out for revenge and insists on talking to Jack face to face.

After Jack convinces Palmer he is not trying to kill him, they go over the "Operation Nightfall" file. The goal of the operation was killing a man named Victor Drazen, and a startling piece of information in the file convinces Jack and Palmer that they are both being targeted. Meanwhile, a scare at the clinic results in Teri and Kim being whisked away to a safe house.

Jack learns that one of the assassins, Alexis Mecir, is actually Victor Drazen's son and has become intimate with one of Palmer's aides. In an attempt to find the man ordering the assassinations, the aide agrees to plant a tracking device in Alexis' wallet. Back at the safe house, Teri and Kim discover their location is no longer secret or safe.

A new U.S. President has negotiated Jack's release from a Chinese prison so Jack can stop a series of terror attacks... with his life.

Can Jack and an unlikely ally stop a suicide bomber and track the architect of these acts of terror?

Jack and former terrorist leader turned peacemaker, Hamri Al-Assad, track a suspicious man to a self-storage facility.

While Jack has problems with Curtis, CTU discovers a nuclear threat and raids a terrorist warehouse, and a shocking explosion shakes LA.

Four more "suitcase nukes" are out there, and Jack's only lead takes him to the home of his brother.

Jack finds himself confronting his father while the lead terrorist needs help if he's to explode the remaining bombs.

Family troubles: Jack with his brother and father while Morris worries about his own brother.

The President meets with a known terrorist, while Jack searches for Morris, Fayed seeks a trigger, and Tom Lennox makes a choice.

Jack looks for a Russian national as his father plots with shadowy patriots. Meanwhile, the President and the Constitution may be in danger.

While Jack looks for Gredenko and tries to save Josh, White House intrigue deepens.

The search for Gredenko finds Jack hunted inside the Russian Consulate and a former President calling on his ex-wife.

CTU's satellite tracking system is compromised as a bomb-carrying drone heads toward an unknown city. Meanwhile, US forces prepare for a nuclear retaliation on the Middle East.

Jack enlists the help of an autistic man in the search for Gredenko, and Sandra Palmer makes a fateful decision.

Jack baits Fayed with Gredenko, while the President faces a challenge to his office.

To find the remaining suitcase bombs, both Jack and the President set up bluffs.

The Chinese want Jack to give them Russian nuclear technology, and the President wants the Vice President's resignation.

Jack goes rogue to save a woman, and the White House needs a fall guy for Fayed's success.

A missing computer circuit board: the Russians get wind of Chinese espionage, the White House must find a leak, and CTU interrogates an unlikely witness.

Russian ire worries the White House, while the Chinese take on CTU, and the damaged circuit board is in surprising hands.

Russia presses the White House, while Jack must try to thwart the Chinese and his oldest antagonist simultaneously.