Street Justice revolves around a U.S. Army soldier turned metropolitan police detective, Adam Beaudreaux (Weathers), and Grady Jameson (Genesse), a martial arts expert. As a child, Grady saved Adam's life when he was wounded in Vietnam. After the encounter, the two never saw each other again and when Adam became a cop, he vowed to find the boy who saved his life. He eventually finds Grady and discovers that Grady's parents, who were Canadian missionaries in Vietnam, were killed and the boy was left to fend for himself.
Adam gets Grady a job at a bar he owns with his friend, Malloy (Fernetz). Grady soon begins helping Adam on cases using the knowledge he picked up living on the streets along with his martial arts training.