African-American Philadelphia police detective Virgil Tibbs is arrested on suspicion of murder by Bill Gillespie, the racist police chief of tiny Sparta, Mississippi. After Tibbs proves not only his own innocence but that of another man, he joins forces with Gillespie to track down the real killer. Their investigation takes them through every social level of the town, with Tibbs making enemies as well as unlikely friends as he hunts for the truth. A black Philadelphia police detective is mistakenly suspected of a local murder while passing through a racially hostile Mississippi town, and after being cleared is reluctantly asked by the police chief to investigate the case.