The Alfred Hitchcock Hour - Season 2 Episode 15 Night Caller

Marcia Fowler accuses a neighborhood boy named Roy Bullock of being a peeping Tom. Roy denies it and manages to ingratiate himself with Marcia's husband, Jack, and her lonely stepson. When Marcia gets an obscene phone call she tells Jack that it was Roy, but he denies it. Later, after Jack goes away on a business trip, Marcia confronts Roy after receiving another obscene phone call and becomes fearful that Roy is crazy when he tells her that his mother was just like her.