一个人的武林

孔武有力的夏侯武（甄子丹 饰）曾是佛山武馆合一门的弟子，当年他争强好胜，在香港担任教官时与他人比武，结果失手将对方打死最终锒铛入狱。三年后的某天，闹市街头发生一宗离奇车祸，死者似乎在车祸前就被武功高强之人残忍杀害。夏侯武在狱中看到该新闻，心知在此背后有一场针对武林中人的猎杀正有条不紊地展开。他强烈要求面见重案组总督察陆玄心（杨采妮 饰），由于言中接下来命案的遇害者，终于取得陆督察的信任，得以协助警方办案。与此同时，先天残疾却练得一身绝技的封于修（王宝强 饰）四处挑战隐于闹市的高手，更在获胜后将他们无情杀害。 　　武林波涛汹涌，夏侯武和封于修迎来对决的终极时刻……A vicious killer named Fung goes around Hong Kong killing top martial arts exponents and leaving a secret weapon called the Moonshadow as his calling card. When a convicted killer and kung fu expert named Ha - formerly working as a martial arts instructor before accidentally killing a man and being imprisoned and convicted for the crime he didn't intend to do - hears of this, he offers to help the police catch the killer in return for his freedom. With Ha's help, the police realize from the chronological order of the victims that the killer is targeting his victims, all top masters in their respective martial arts style, and following a martial code of training. After a close encounter with Fung, Ha suddenly disappears and the police begin to suspect the worse: that the two are accomplices and Fung was the bait to help spring Ha from jail. But Ha has actually gone back to his home in Foshan to find out more about the mysterious calling card. While doing so, he discovers the killer's identity and his motivation: the true philosophy behind Fung's martial arts is to kill opponents who are weaker than him. Steadfastly, Ha refuses to be drawn into a fight with Fung - until the killer threatens the woman he loves most. Only then does he realize that he would have to go against the martial code in order to uphold it.