影片的男主角基顿（巴斯特·基顿 Buster Keaton 饰）是一名乡村影院电影放映师，他喜欢阅读侦探类的书籍，经常幻想自己就是一名像福尔摩斯一样的大侦探。一天，他把价值一元的巧克力糖谎称四元送给女友凯莎琳（Kathryn McGuire 饰），不料被情敌趁机陷害，说基 顿偷了别人的手表拿去当才有钱买巧克力。凯莎琳相信了谗言，遂将基顿赶出门外，并取消了二人之间的婚约。基顿查访之后，发现情敌才是偷表典当的家伙，但却苦无证据洗清冤情。某日，基顿在放映电影时，发现银幕上的故事竟和他的遭遇同出一辙，而且人物也雷同，唯一不同的是电影中的故事发生在一个上流家庭而已。基顿边放映电影边沉溺在电影之中，于是走出放映室，从观众席走入银幕之中逮捕情敌罪犯。可是进入银幕后的基顿却四处碰壁，一筹莫展．随着场景的变化，银幕上的映象不断从幻想变成事实……

　　This very Kafka-esque film is Keaton's response to the Fatty Arbuckle scandal.[citation needed] Even though the central character's intentions are good, he cannot win, no matter how inventively he tries. He gets into various scraps with police officers throughout the film. Eventually, he unwittingly throws a bomb into a police parade and ends up being chased by a horde of cops.　　At the end of the film, Keaton's character locks up the cops in the police station. However, the girl he is trying to woo disapproves of his behavior and gives him the cold shoulder. Therefore, he unlocks the police station and is immediately pulled in by the cops. The film ends with the title "The End" written on a tombstone with Keaton's pork pie hat propped on it.　　One of Keaton's most iconic and brilliantly-constructed short films, Cops was deemed "culturally, historically, or aesthetically significant" by the United States Library of Congress and selected for preservation in their National Film Registry in 1997.