法兰克是一个年轻而富有理想的警察,他从巡警开始做起,后来成为卧底警察,虽然他的破案率很高,但他不愿意象其他警察那样收受贿赂,这使他显得和其他人格格不入。这种做法也使他身陷危机,因为他的同事们都与他为敌,且不时地陷害他。当检察组开始调查警局内部的贪污内幕时,他又出面作证,因此更陷入危险之中……Serpico is a cop in the 1960s-early 1970s. Unlike all his colleagues, he refuses a share of the money that the cops routinely extort from local criminals. Nobody wants to work with Serpico, and he's in constant danger of being placed in life threatening positions by his "partners". Nothing seems to get done even when he goes to the highest of authorities. Despite the dangers he finds himself in, he still refuses to 'go with the flow', in the hope that one day, the truth will be known.