吴奇隆和金城武在警界各司其职，一个是飞虎队队员，另一个是交通警察。因一次银行抢劫案中，两人阴差阳错成为拍档，更成为香港打击罪犯的新希望，因而触怒了犯罪集团，视他们二人为眼中钉。此时警方突然接获密令要二人保护中共高干之女儿白美红（杨采妮），于是两人乔装进入学校，作贴身保护。犯罪集团三番四次出手，皆不能得逞，于是使出杀手锏将红掳走，不料原来红亦是冒牌货。而犯罪集团就在这两名“猛警”与红的误打误撞下被瓦解。

A high school loser dreams of winning the heart of the principal's daughter, but his chances are slim as long as her bruiser boyfriend's around. Fortunately, a chance meeting with Garlic and Gimmick, renegade cops who cause nothing but headaches for their superiors. Chief Wong Yat Fei decides to send his boys undercover in Wong Fei Hong College to protect a general's daughter from Mainland China, but that's where their problems begin. Their boyish good looks may fool their classmates, but how will the two undisciplined cops pass their classes, let alone protect a girl who's tougher than they are?