Danny, a respected cop, is setup after an investigation goes wrong. While laying low in his new jail cell, Danny is forced to get involved in the inmates underground cage fighting circuit. With the help of Irving, a former mixed martial arts champion, Danny devises a scheme to bring justice and innocence to his family's name, if he can get out of the cage alive.

香港是个投醉繁的社会,一个有钱有势在黑白两道,可说呼风唤雨的黑道老大孔老二与另一帮派军火走私犯龙武,在相争地盘势力下展开一场生死战.有一次从上海偷渡来港的杜生投靠孔老二加入感情,为了义气,为了金钱而犯了绑票案.在监狱内得知女友秋华为决心戒毒瘾而被孔老二杀害。