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？
To the streets, “Raq” Thomas is cold, hard and fierce — a successful and deadly woman taking names in a man’s world. She is tough, resolute, ruthless, but Raq still is capable of love. Great love. The sole recipient of that affection is her son, Kanan; he is everything to her. As much as she cares for him, though, there are many instances where one wonders if she loves him for who he is or if she loves him merely as an extension of herself. The middle child of three, Raq also carries the heavy burden as the earner for her two brothers. She is the sun, and everyone else in her universe exists in her orbit.
