徐夕(李连杰)本是神秘杀手组织701部队里的一名冷血杀手,因为不想再做杀人工具,他逃离了该组织来到香港化身为一名普通的图书馆理员,因此结识警察石SIR并与之成为好友,不想701部队为追杀黑帮头目突然现身香港,一时石SIR及警方均束手无策,见好友处于危难中,徐夕挺身而出化 为黑侠。 黑侠让701部队的首脑熊菊(龙刚)大为震怒,遂派徐夕旧情人若兰规劝黑侠归顺,被徐夕断然拒绝,结果令图书馆除Tracy(莫文蔚)之外的诸同事皆丧命。为保护Tracy,徐夕再做黑侠采用强硬态度要带她走,遭不知黑侠就是其意中人徐夕的Tracy的拒绝。后在与熊菊一干人等对抗的过程中,徐夕渐从Tracy身上寻到自己想要的情感。Micheal, a former test subject of a project to create supersoldiers, is forced to escape with his comrades after the project was cancelled. Months later, he is trying to have a quiet life as a librarian with a tough cop as his best friend. However, a string of vicious gangland murders begins that has all the markings of his former compatriots who seem to have turned to violent crime. Realizing that the police are helpless to fight these soldiers, Micheal decides to take them on himself. Donning a mask to protect his identity, Micheal must fight these powerful villians as the mysterious superhero known only as Black Mask.