1第 1 集

一具感染了致命病毒的尸体被扔在了洛杉矶卫生中心外面。Tony和Michelle结了婚，并且已是CTU的主管。他接到了来自一个名为Hector Salazar的墨西哥毒枭的恐吓，他声称如果不把他的哥哥Ramon释放，会有更多的人感染上这种病毒。事实上，Ramon是Jack通过做卧底抓回来的。就在Jack和他的新搭档Chase审问Ramon时，Ramon杀死了自己的律师，并且对Jack他们说了一些奇怪的话。Palmer总统还活着，并且三年来首回洛杉矶，目的是参加新一轮总统竞选的辩论会。他的弟弟Wayne成了他的首席助手，而他的私人医生Anne Packar成了他的女友。一个名叫Kyle Singer的年轻人拿着一包看似毒品的白色粉末，他晚些时候要把这包东西送到交易人的手里，而同时Salazar的手下正在监视Kyle。Kim此时也在CTU工作，并且和Chase交往了三个月。Kim决定在今天把这件事告诉Jack，但是Jack似乎染上了毒瘾

2第 2 集

Jack and Chase quarrel over Chase's relationship with Kim. Meanwhile, they learn of a lead to the possible whereabouts of the virus after rading a crackhouse. Linda breaks up with Kyle when she learns that he is planning to make a drug delivery. Wayne approaches Palmer with information about his girlfriend that could damage his chances for reelection, while a CTU employee is not what he seems.

3第 3 集

Jack and Hector both search for Kyle, while Chase finds himself out of action at CTU. Wayne and Palmer argue over the implications of Anne's past, while Ramon takes out one of his opponents in a surprise move. Tony leads an operation to get Kyle, but tragedy strikes when Salazar's man gets there first.

4第 4 集

在Tony受伤之后，Michelle忍着伤痛接手Tony的工作。Kyle和Linda最终被Hector的手下关押起来。Jack秘密联系 Palmer总统，请求允许他劫狱来拯救百万人的生命，Palmer总统默许。由于Chase的插手，Jack的劫狱计划遭到了意外。在Anne的劝阻下，Palmer总统拒绝向Anne前夫的勒索妥协。

5第 5 集

Jack's efforts to break Ramon out of prison go awry when they are captured by a group of inmates during the riot. Chloe unwittingly stumbles on to Jack's drug problem and she is forced to reveal his secret to Kim and Michelle. Palmer begins his debate with Keeler, while Kyle prepares to sacrifice himself to save Linda.

6第 6 集

Jack and Ramon struggle to evade the authorities, while Palmer must shut the debate down because of the prison break. Kim accidentally stumbles on to Gael's secret communications, but she isn't able to warn Michelle in time. The Singer family learns a startling piece of news about Kyle's health.

7第 7 集

在飞往墨西哥的飞机上，Ramon把Jack监禁了起来。在Ramon想杀死Jack的紧要关头，Jack成功地逆转局面，反而把Ramon扣为了人质。在飞机抵达墨西哥后，Ramon才得知一开始Jack和Hector就达成了协议，设法把Ramon从监狱中弄出来。Gael被CTU逮捕。正当 Chappelle审问Gael的时候，Tony从医院回来，宣布他和Gael以及Jack在进行一项秘密的病毒拦截活动，而Gael和Jack所做的一切都是这个计划中的一部分。Anne接到前夫的电话，要她去他那儿取她无罪的证据。与此同时，Chase独自一人正前往墨西哥营救Jack。

8第 8 集

Palmer and Chappelle view a message from Jack, explaining his undercover work with the Salazars. Meanwhile, Hector tries to convince Ramon that they should deal with Bauer so that they can get their hands on the virus. Jack has a private moment with Claudia and she blasts him for leaving her behind when he arrested Ramon. Chase arrives in Mexico, but is captured by Hector's men. Ramon devises a way for Jack to prove his loyalty to them. Anne manages to clear Palmer's name, but she breaks off her relationship with him.

9第 9 集

Palmer clears Anne's name with the press, but he finds that he is facing a new problem when his biggest campaign contributer reveals a startling secret about Wayne. Kim and Michelle worry about Tony's mental ability when he continues to make mistakes. Jack and the Salazars meet with Amador, but the deal turns sour when Nina Myers appears on the scene and competes for the virus.

10第 10 集

Claudia manages to free Chase from his captors, but she pays a high price for her efforts. Wayne turns to Julia, while Palmer calls on Sherry for help against Milliken. Jack and Ramon make plans to get to Nina, in the hopes of intercepting the virus. Chloe's work at CTU is disrupted when she is forced to take care of her baby.