这一季的故事发生在上一季的3年后。这一季里,托尼(卡洛斯·博纳德 Carlos Bernard 饰)和米歇尔(蕾可·艾尔丝沃斯 Reiko Aylesworth 饰)结婚了,并且成为了CTU的主管,而杰克(基弗·萨瑟兰 Kiefer Sutherland 饰)的女儿金姆也加入CTU成为了一 名情报分析员。剧情由一具被扔在洛杉矶卫生中心外并感染了致命病毒的尸体开始。一个墨西哥毒枭为了让美国政府释放自己的哥哥,以致命病毒为恐吓。杰克也因此又踏上了反恐调查之路。而这一季里面,杰克的调查并不顺利,为了打入毒贩内部,杰克不惜染上毒瘾,这导致他在调查中困难重重。而白宫方面,获得连任的鲍尔默总统(丹尼斯·海斯伯特 Dennis Haysbert 饰)康复后身边多出了一位私人医生女友,而总统的弟弟韦恩成为了他的得力助手,在连任压力面前,又要化解这场生化危机。总统还能像前几次那样给予杰克强有力的支持吗?
Kaewsai just graduated from Faculty of Communications and started working at a broadcast station owned by Mutthana, who is her father's lover. Her parents got divorced when she was a child and she was raised by her grandparents. Mutthana had only one son, Siwa, who is arrogant and hates Kaewsai's father because he thinks that he stole his mother's love. Siwa came back to Thailand after studying abroad for many years and meets Kaewsai in a party. He's impressed with her strong and smart personality, but starts to hate her after he found out who her dad is.
Kaewsai has to prove herselft to everyone who thinks she only got work at the station because of her connections, while facing many mean and selfish people. Other executives at the station have a grudge against Siwa's mother so he also has to prove himself when he's cast as the main actor in a lakorn directed by Kaewsai. He starts to fall in love with her unexpectedly, and she also falls for him after they get close.