Third Degree Burn

Scott Weston (Treat Williams) makes a living investigating other people's private lives. One day, successful businessman Clay Reynolds (Richard Masur) hires him to follow his wife, Anne (Virginia Madsen), because Clay isn't entirely convinced that she's faithful to him. Scott's surveillance eventually turns into attraction, and he and Anne begin a steamy love affair behind unsuspecting Clay's back. When Clay mysteriously winds up dead, all clues point to Scott as the murderer.