The characters in In the Heat of the Night by John Ball include the protagonist, Virgil Tibbs, and the local police officers in the small Southern town of Wells that Virgil is visiting. When the book opens, Maestro Enrico Mantoli has been murdered. He had come to the town to start a music festival.
As the foreword to the book notes, Virgil Tibbs “happens to be passing through a southern town at a particularly inauspicious moment.” There has been a murder, and the local police arrest Tibbs, who is black and a stranger. It turns out, however, that Virgil is a reputable homicide detective back in his hometown in Pasadena, California. He is called in to help the local police solve the murder.
Sheriff Bill Gillespie is the chief of police. He enlists Virgil's help to solve the murder. Sam Wood is one of the police officers who reports to Bill Gillespie. He appears to be a racist. The author writes,
Sam took immediate command. “On your feet, black boy,” he ordered, and crossed the room in five quick steps.
It turns out that the man Sam has arrested is Virgil Tibbs. When Sam takes Tibbs back to the station, Chief Gillespie questions Virgil about what he does for a living. It comes out that Tibbs is a fellow police officer:
“And what do you do in Pasadena, California, that makes you money like that?”
The prisoner took the barest moment before he replied.
“I’m a police officer,” he said.
Pete and Arnold work in the sheriff’s office and report to Bill Gillespie. They are both somewhat surprised by the way Chief Gillespie seems to have Virgil Tibbs take control of the investigation into Mantoli's murder. Mantoli has a daughter who also figures in the story.
Harvey Oberst is the first suspect that Chief Gillespie’s men arrest, because he was caught with Mantoli’s wallet. However, after questioning him, Virgil is convinced that he is not guilty.
Dr. Harding is an “elderly Negro who carried a black bag” and ministers to the physical needs of the black citizens of Wells.
Delores Purdy is a sixteen-year-old neighbor of Harvey Oberst’s. Harvey is caught with her, which adds to Chief Gillespie’s rationale in having him arrested for the murder.