Chan Wing Yan, a young police officer, has been sent undercover as a mole in the local mafia. Lau Kin Ming, a young mafia member, infiltrates the police force. Years later, their older counterparts, Chen Wing Yan and Inspector Lau Kin Ming, respectively, race against time to expose the mole within their midst.

1990 film by Wong Kar-wai

2007 film by Derek Yee

1999 film by Johnnie To

20世纪90年代初，香江怒海，一代枭雄倪永孝（吴镇宇 饰）雄霸黑道，风头无两。以此为契机，青春年少的警校学生陈永仁（余文乐 饰）肩负机密使命潜入黑道，从此开始了他无法回头的黑暗人生。与此同时，精明狡猾的黑道头目韩琛（曾志伟 饰）密令弟子刘建明（陈冠希 饰）考入警校，成为他日后纵横江湖最重要的一枚棋子。转眼十年，风云变幻。韩琛早已成为新千年的黑道霸主。一起毒品交易的攻防战，令他和黄督察（黄秋生 饰）都敏锐地察觉到“内鬼”的存在。 在此之后，刘建明（刘德华 饰）与陈永仁（梁朝伟 饰）展开连番紧张危险的卧底角斗。经历无数腥风血雨，在无间地狱求生、痛苦片刻不停的二人不仅面临最终对决，还将用毕生品味命运所施加的苦果……

2001 film by Johnnie To, Wai Ka-Fai