Jersey is a popular gambler in Mongkok. One day, he takes a trip to Japan with her girlfriend, Nancy, they come to Chinese resaurant. Suddenly, a gang of Japanese triads comes in and starts a fight. Just at the moment when he is in danger, the restaurant owner uses a special card - casting skill to save him. Jersey recognize it is the skill of Cool, the Gambling King, but the owner refuses to admit that Cool is still alive. Cool finally admit his true identity and tells Jersey that Ho Yan was orginally his girlfriend but now she is the wife of Yeung. Cool treated Yeung like his brother, but he is jealous of Cool's beautiful grilfriend and wealth. Yeung conspired to take away Cool's everthing. With Jersey's help, Cool decides to get Ho Yan back, but he does not realizes that Yeung is setting another trap for him.

An operation in Thailand against a notorious drug lord changes the destiny of a Hong Kong Police Department narcotic team. Five years later, a drug dealing brings them together again.

21世纪特种部队人员项少龙（古天乐 饰）决意要参加穿梭时空的研究，是为了要挽回自己的爱情。但由于时光机的数据出错，把少龙带到了战国时期。
当时的嬴政（林峰 饰）还没有登上帝位，更被囚禁于赵国。少龙为了能返回未来，便不惜一切帮助嬴政顺利登上帝位。由于少龙的机智过人与特殊身份，他的能力得到了众人的赏识，因此他也遭到了多方奸狡之人的暗算。
在腹背受敌的情况下，生性风流的少龙也纠缠上一段复杂的四角恋爱关系。到底少龙能否协助嬴政赢得天下呢？他会如何处理自己与隔世恋人的情缘呢？

2004 film by Johnnie To