Jack's dejected mourning is interrupted by a call from President Palmer, who needs him to foil another terrorist plot.
Jack finds his loyalty challenged when he returns to work to re-establish his cover.
While undercover, Jack is recruited for a lethal assignment. Megan needs help to escape her father's violence. Kate finds proof of Reza's terrorist ties.
Jack gets closer to the man behind the explosion. The woman behind his wife's death is linked to the LA bombing. George Mason has radiation poisoning, but goes back to work regardless.
The Ambassador requests an information exchange, which the President begrudgingly agrees to. Tragedy strikes before the President can get their side of the exchange. Jack demands to be put on the interrogation.
An hour of interrogations as Jack tries to get information out of Nina and Tony questions Reza.
While President Palmer worries about conspiracy, Jack takes Nina to California in the hopes of stopping the terrorists.
Nina and Faheen speak in Arabic which leaves Jack and Michelle scrambling to find hidden meanings and hopefully the bomb's location. Kim deals with police about the body discovered in the stolen car's trunk.
Jack and Nina survive the plance crash but in the chaos that ensues, Nina gets the upper hand on her captor.
In a Presidential address, Palmer alerts the country to the possibility of terrorist action in Los Angeles. Nina attempts to outstep Jack's vengeance.
Jack escorts Kate to a mosque hoping to uncover a terrorist. Roger Stanton's continued assignment is in jeopardy.
Jack will stop at nothing to get information out of Ali and even uses Ali's family as leverage.
Jack and Kate try to discern Marie's rationale. Lynne takes a stand against Sherry Palmer.
There is a shakeup in CTU leadership. Jack thinks that he may have stumbled upon a critical clue.
Jack has a difficult discussion with Kim over the telephone. Kate wonders how she could let Marie do what she did.
Kimberly fears the worst when she seems a looming mushroom cloud. The President balances the decision to launch an invasion force.
Jack tries to discern the whether the Cyprus tape is authentic while the President and Vice President debate military strategy.
President Palmer readies the army should they need to quell any activities in the recently nuked California. Jack tries to rescue Wallace who is the key to stopping wrongful military aggression.
Jack continues to try to prove the Cyprus tape a fake. President Palmer balances the attack decision. Tony investigates the bad rapport between Michelle and Carrie.
Jack endures near-fatal torture in trying to protect the technology that will prove the Cyprus recording inauthentic. Tony is put to the task of running intelligence for a military campaign.
The clock is ticking as Jack and team try to use the computer chip he's secured to stop the potential war. Meanwhile, President Palmer squares himself against opposition from his cabinet.
Jack tries to bring in the mastermind behind the fake Cyprus tape. Tony puts his future in danger to aid Jack. President Palmer brings a crucial player over to his side.
Jack tries to protect the person who can stop the war from coming into fruition. Palmer seeks information on Peter Kingsley, the man behind the computer hacker.
Jack turns to Sherry Palmer to unmask Peter Kingsley's involvement in the faked Cyprus recordings through a hidden mic and a meeting at the Los Angeles Colliseum. Kate and Bob visit Marie in her confinement. At a public address, the President is attacked by Mandy who works for a mysterious benefactor.