Protagonist of the film is Shale (played by Tom Berenger), Vietnam veteran and top mercenary who used to conduct all sorts of clandestine operations for CIA. After the botched job in Cuba he, together with small band of comrades, is forced into retirement. He goes to Miami where he would like to settle down with his girlfriend, high school history teacher Janet Hetzko (played by Diane Venora). After Janet has her knee broken by assailants, Shale is determined to find the reasons behind it and suspects that they are connected with her job in drug-infested high school. It turns out that Janet tried to have one of her pupils, Juan Lacas (played by Marc Antony) kicked out of school, and that was something Lacas, who led drug-dealing gang "Kings of Destruction" didn't particularly like. In order to get to the bottom of this, Shale falsifies records and enter school posing as Janet's substitute. There he finds Lacas and his gang as nothing more than tiny part in well-oiled drug-dealing machine connected with organised crime and corrupt local government. Realising that his military skills aren't enough to defeat the drug dealers, he calls his comrades to help him, which would result in spectacular and violent confrontation.

Idea of a covert operative infiltrating high school posing as a substitute teacher seemed so far-fetched that few critics took it seriously. This was good thing, because otherwise THE SUBSTITUTE would have been savagely attacked for promoting violence and vigilante justice. Thankfully, people behind this film took their job seriously. The script is, if we disregard the basic idea, well-written and the characters in the film are believable. The diverse cast (that includes Latino pop star Marc Antony), made of reliable character actors, does its job very well. Berenger is also quite effective in the role that gave him rare opportunity to play an action hero. Director Mandel in the end mishandles the final showdown by not lighting it. Yet, that darkness in the end would do little to the generally nice impression of THE SUBSTITUTE, one of those hidden 1990s gems that could be a guilty pleasure for much bigger audience than those nostalgic for the times when Charles Bronson used to solve social problems.