一对热血虔诚的爱尔兰裔兄弟，因自卫杀人而得罪黑帮，警署以正当防卫之名无罪释放。从此之后，二人决定以己之力对抗社会渣滓，购买武器以暴制暴，在朋友洛克（大卫·德拉·洛克David Della Rocco 饰）的帮助下清除犯罪分子。联邦警探保罗·斯迈克（威廉·达福 Willem Dafoe 饰）负责侦破案件，本来毫无头绪；但 在黑帮头子“老爸乔”（卡洛·罗塔 Carlo Rota 饰）雇佣了传奇枪手“公爵”（比利·康诺利 Billy Connolly 饰）对抗麦克马纳斯兄弟之后，情况却发生了意想不到的变化……
波士顿，一位深受爱戴的牧师神秘被杀，子弹交错穿过脑壳，死相极为惨烈，传言处刑人所为。负责此案的依旧是警察格林利、达菲和多利，但他们对此一筹莫展。幸有智慧性感的FBI特工尤妮斯・布鲁姆（朱莉•本茨 Julie Benz 饰）破解了处刑人的杀人手法。因10年前波士顿血案，异卵双生兄弟康纳（肖恩•派特里克•弗兰纳里 Sean Patrick Flanery 饰）和墨菲（诺曼•瑞杜斯 Norman Reedus 饰），随领袖父亲诺亚（比利•康诺利 Billy Connolly 饰）隐居在爱尔兰的乡村。此案一出，两兄弟削发明志，重新出山。期间，他们收服了墨西哥人罗密欧（小克利夫顿•克林斯 Clifton Collins Jr. 饰）。后者凭借机灵的头脑、出众的拳脚，战胜了人高马大的对手。虽然将对手置于死地有些残酷，但是兄弟俩觉得对味，并设计拉他入伙。这组搭档与美女特工都踏上征讨处刑人的危险之旅……
Sometime in the near future, paraplegic prison inmate Matt Mills meets The Board of Satoshi-Telefair Industries, who thank him for joining the Program. Under pressure and with a promise to make him walk again, Mills agrees to volunteer. He is injected with a synthetic nanomaterial and suffocated, only to wake up with restored use of his legs, yet alone in a steel cell in the first spoke of an experimental apparatus - The Wheel. A series of assailants inflict a multitude of damage to Mills' body and torment his mind, yet the synthetic nanomaterial not only restores his damaged organs, it re-engineers his strength. The experiment might be designed to kill, but Mills is determined to survive - and get back to his daughter before The Board finds her first.
