Virgil Tibbs
Virgil is a police detective from Philadelphia who is trying to catch a morning train out of Sparta for home when Sam Wood, a local deputy, arrests him. Virgil is arrested for being black and accused of murdering Colbert. Sheriff Gillespie learns that he is an ace homicide detective and asks for his help in solving Colbert's murder. Virgil reluctantly helps him and must overcome the still racist and violent actions of the people of Sparta, Mississippi to find the real killer.
Gillespie
Gillespie is the Sheriff in Sparta, Mississippi. He questions Virgil about the murder of Colbert until he learns he is a police officer. Ironically he asks Virgil to help solve the murder of Colbert and the two become an unlikely pair as they seek to find the truth.
Sam Wood
Wood is the deputy who wrongly arrests Virgil, believing he's Colbert's murderer simply for being a black man who doesn't live in Sparta. Wood becomes a prime suspect before he's cleared by Virgil. Sam has gotten a 16-year-old pregnant and is at the center of the Colbert murder because of his immoral actions.
Endicott
Endicott owns and operates Endicott Cotton Company. He is an "old boy" Southerner who wishes he could still kill black people just because he can. He comes off as a plantation owner who believes he's doing the best for black people as if he's training them up in some sick way. Virgil believes him to be a prime suspect in the Colbert murder as a rare fertilizer that Endicott uses was found near Colbert's body.