At the beginning of the season Sylvia becomes pregnant with Andy's child. A baby boy, Theo, is born towards the end of the season. This is contrasted with the fate that awaits Sipowicz's older son, Andy Jr., who announces that he is to join the police force. Andy is finally bonding with his estranged son when he is gunned down, which leads the elder Sipowicz to fall off the wagon. Andy Jr's murderers are killed themselves by Simone in an act of self defense.
Bobby and Diane, whose relationship had been put on hold while she attended AA, resume their relationship only for Diane to begin drinking again when her abusive father beats her mother. Her father is eventually killed and her mother becomes the prime suspect.
James Martinez and new detective Adrienne Lesniak begin an affair but only after Lesniak tells Medavoy that she is gay, then that she is not; Martinez later breaks up with her due to her controlling and unpleasant behavior, and Lesniak eventually leaves the squad. Medavoy himself leaves his wife, recognizing that she is holding him back but it is too late to save his relationship with Donna who leaves to take up a job with Apple.
一场火车对撞的惨剧夺去131名乘客的性命,大卫•杜恩(Bruce Willis 布鲁斯•威利斯 饰)奇迹般地成为这场灾难过后的唯一幸存者,且浑身上下毫发无伤。在他参加遇难者追悼会之后,他在车窗上发现一张神秘便条,写道:“你这一生生过几次病?”
不久,一个名叫伊利亚•普莱斯(Samuel L. Jackson 塞缪尔•杰克逊 饰)的黑人出现在大卫面前。和大卫不同的是,伊利亚天生手脚残废,脆弱不堪。喜爱漫画的伊利亚认定大卫就是书中那种具有超自然能力的超人。懵懂的大卫开始在伊利亚的引导下认识自身的能力……