Wealthy industrialist Phillip Colbert moves to Sparta, Mississippi, to build a factory there. Late one night, police officer Sam Wood discovers Colbert's murdered body lying in the street. Wood finds Virgil Tibbs, a black man with a fat wallet, at the train station and arrests him. Police chief Gillespie accuses him of murder and robbery but soon learns Tibbs is a top homicide inspector from Philadelphia. Tibbs wants to leave town on the next train, but his boss suggests he stay in Sparta to help with the murder investigation. Though Gillespie, like many of Sparta's white residents, is racist, he and Tibbs reluctantly agree to work together.