机灵活泼的穷小子小山（汪禹饰）游手好闲，又好赌，整天过着坑蒙拐骗的日子，生性顽皮，喜欢捉弄人，因此惹下连连祸事。一日，小山偶遇落魄的流浪少年凯云（刘家辉饰），凯云失去记忆，空有一身好功夫，两人成为朋友，联手把一帮坏人打得落花流水，帮助了很多贫苦百姓，闹出了诸多趣事。凯云的大官父亲带着保镖（刘家荣饰）前来寻找儿子，引出重重误会；另一方面，小山与凯云遭到那帮坏人的追杀，最后凯云恢复记忆，与小山联手把坏人一举成擒！

　　本片外借汪禹、刘家辉两大邵氏最当红的武打小生联袂主演，武打精彩，剧情轻松活泼，笑料百出，为不可多得的功夫喜剧佳作。

He's lost his memory, but not his skill: After a fierce battle with a local tong, Hoi is thrown over an embankment and left for dead. He survives the ordeal but has lost all of his memory, but not his kung-fu. His fateful meeting with a beggar leads to their teaming up for cleaning up that tong.