余小宝（黄秋生 饰）是一个练有独门绝技的一代宗师，但是因为年龄的增长和中年发福，让他逐渐力不从心，只能依靠经营铁打医馆讨生活。因为妻子早亡，余小宝既当爹又当妈的照顾儿子和女儿，但是两个孩子却总是吵架，从小练武的两人经常在饭桌上就打起来，最后打翻一桌子的菜。青春期后，孩子们都厌烦父亲不停说当年的英勇，因为看着啤酒肚的父亲他们无法想象。哥哥一直喜欢妹妹的好朋友，但是好友已经有一个音乐人男友了。

  特工Rocco当年在执行一场暗杀的时候，因为没有留意背后被偷袭，导致脊椎被拧断半生都瘫痪，只能在轮椅上面生活，经过他的调查知道对自己下手的是戴子龙，但是他早就应改名换姓人间蒸发，经过调查知道余小宝知道戴子龙的下落。Rocco绑架了余小宝要求他说出戴子龙的在哪里，两个孩子联手解救父亲。

Yu Xiaobao (Anthony Wong) is a master of a generation who has practiced unique skills, but due to age and middle-aged , so that he was gradually unable to do what he wanted, and could only rely on the operation of the iron hospital to make a living. Because his wife died early, Yu Xiaobao was both a father and a mother to take care of his son and daughter, but the two children always quarreled. The two who practiced martial arts since childhood often fought at the dinner table, and eventually knocked over the dishes on the table. After puberty, the children were tired of their father's constant talk about his bravery, because they couldn't imagine his father with a beer belly. The elder brother has always liked the good friend of the younger sister, but the friend already has a boyfriend who is a musician.

When Agent Rocco was carrying out an assassination, because he did not pay attention to the The sneak attack caused the spine to be twisted and paralyzed for half his life, and he could only live in a wheelchair. After his investigation, he found out that Dai Zilong was the one who attacked him, but he should have changed his name and disappeared long ago. After investigation, he found that Yu Xiaobao knew Dai Zilong's whereabouts. Rocco kidnapped Yu Xiaobao and asked him to tell where Dai Zilong was. The two children joined forces to rescue their father.