When a prostitute is murdered in San Francisco's ritzy Nob Hill district, an anonymous tip implicates minister and political crusader Reverend Logan Sharpe (Martin Landau). Lt. Virgil Tibbs (Sidney Poitier), who has known Sharpe for many years, asks to be assigned to the case in hopes of clearing his friend's name. So begins the detective's journey through a twisted maze of baffling evidence, frantic chases, deadly gun fire and bad alibis. Before long, Tibbs finds himself bitterly torn between his duty as a cop and his loyalty to a friend.