Virgil Tibbs is a Philadelphia Homicide detective home to see his mother in the rural south. He is arrested on general principles when a rich white man is found dead, and Tibbs' being Black is enough reason. When his identity is established, his boss offers his services to the small town sheriff who has little experience with murder investigations. As the two policemen learn how to work together, they begin to make progress on the crime. After a wealthy northern factory owner is murdered, racist Mississippi cops accuse African American Virgil Tibbs (Sidney Poitier) of the crime. Once they learn that he is a renowned Philadelphia homicide detective, they reluctantly seek his help. As Tibbs displays his skills as a detective, he begins to win the respect, protection, and ultimately friendship of the Police Chief Bill Gillepsie (Rod Steiger).