<P> Tibbs and Gillespie accompany Wood on his patrol route, stopping at a diner where the counterman, Ralph, refuses to serve Tibbs . When Tibbs notices that Wood has deliberately changed his route, Gillespie starts suspecting Wood of the crime . Tibbs indicates that he knows why Sam has changed his route but will not disclose the reason to Gillespie . </P> <P> When Gillespie discovers that Wood made a sizable deposit into his bank account the day after the murder (which Wood claims is gambling winnings) and Purdy, a local, files charges against Wood for getting his 16 - year - old sister Delores pregnant, Gillespie arrests Wood for the murder, despite Tibbs' protests . Purdy is offended that Tibbs, a black man, was present for his sister's interrogation about her sexual encounter with Wood, and he gathers a mob to get his revenge on Tibbs . </P> <P> Tibbs is able to clear Wood by finding the original murder scene, the site where Colbert's factory will be built, and pointing out that Wood would not have been able to drive his police patrol car and the victim's car at the same time . Tibbs also admits that he knew immediately that Wood changed his route not to hide being a murderer, but to hide being a peeping Tom (peeping on Delores, who herself is an exhibitionist), and declined to publicly reveal this in order to spare Wood embarrassment . </P> <P> Acting on a hunch, Tibbs tracks down the local back - room abortionist, who reveals that someone had paid for Delores to have an abortion . When Delores arrives, Tibbs pursues her outside, where he is confronted by the murderer, Ralph . Purdy's mob has tracked down Tibbs and is holding him at gunpoint when he proves to Purdy that it was Ralph, not Wood, who got Delores pregnant . </P>

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