香港小混混乐爷（吴镇宇饰）因欠下50万高利贷躲到了内地的小宝（彭波饰）家里；小宝因爱看黑帮片成天盼着去香港见大明星、入黑社会。为了弄到钱，乐爷策划了俩人行窃某集团董事长王世雄（高军饰）。不料入室后遭遇了冒牌“东南亚第一杀手”的查尔斯（林雪饰），查尔斯为还赌债受雇杀人，而雇他杀人的有几拨人马。王世雄的女儿王诗宜（颖儿饰）在被绑架之时，阴错阳差地被乐爷所救，但她失去记忆、智商低下。纯真而依赖的女孩情怀，令本想用王诗宜进行敲诈的乐爷迟迟未行动。就在乐爷想到了一个既可以拿到钱、又可以保护王诗宜的办法时，幕后真凶杰克（连晋饰）及其手下田基（王太利饰）找到了他们，而杀手查尔斯也找上门来。

The small fry in Hong Kong Yue Ye owed loan sharks 500.000 hide in the home; of the Mainland's Andy Andy to two gangsters like to watch movies all day looking forward to go to Hong Kong to see the big star, into the underworld. In order to get the money, the music God has two people to steal a Planned Group chairman Wang Shixiong. Unexpectedly suffered a burglary to take to the "Southeast Asia's first killer" Charles, Charles employed murder, gambling debts and hired to kill HIM A Few dial troops. Wang Shixiong the daughter of Wang Shi Should kidnapping someone else to the music God rescued, but her loss of memory, low IQ. The feelings of innocence and dependent girl, Wang Shi Yi Yue Ye Extortion delay in action. Thought Either Their money in the music god, but Also to protect the way of Wang Yi Shi, and his murderers behind the fields to find Their killer Charles Came to the door