Mark哥(周润发 饰)和志民(梁家辉 饰)是堂兄弟,两人是越南华侨,现正在香港发展。岂料越战打响,两人都十分担心仍然居住在越南西贡的志民的父亲松叔的安危,为了凑足钱将志民父亲接到香港,两人决定帮当地黑帮走私军火到越南。岂料他们在越南遭到了丧邦的伏击,关键时刻幸亏香港黑帮老大的女友英杰(梅艳芳 饰)及时相救,两人才幸免于难。逃过一劫的三人在西贡渡过了一段快乐时光后,英杰辞别了两人。随后Mark哥和志民将松叔顺利接回了香港。回港后,两人过着安稳平静的生活,只是一直都没有打听到恩人英杰的消息。突然有一天,英杰出现了,重逢令三人都十分开心。只是,一场祸事也在悄悄逼近……
在他们迷失在另一个维度之后,拉泽团队再次联合起来对抗新的威胁。
Based on the novel by Karel Capek, the prominent Czech writer of the early 20th century who coined the word robot for his play R.U.R., the story revolves around a discovery of Krakatit - a powerful explosive - by Prokop, an experimental scientist who, following an accidental explosion in his lab, slips in and out of delirium. When he realises that, in a delirious period, he has given the formula for making Krakatit to one of his colleagues, he tries to find the man, who does not realize how dangerous a thing Krakatit is. In the process, he nearly gives his discovery away again to foreign interests, a group of anarchists, and even greater forces of darkness...