Directed by Fred Walton, When a Stranger Calls (1979) stars Carol Kane, Charles Durning, Colleen Dewhurst and Tony Beckley in a psychological horror film about a babysitter terrorized by threatening phone calls. Expanded from Walton and Steve Feke’s short film The Sitter, the film became closely associated with the “babysitter and the man upstairs” urban-legend premise. Its mix of phone terror, home-invasion fear and stalker horror later led to both a sequel and a 2006 remake.

Based on the infamous urban legend and featuring one of the most famous and gripping opening scenes in horror movie history (homaged by Wes Craven in the opening of Scream), Fred Walton’s When a Stranger Calls is a masterclass in suspense that has rarely been equalled.

A student babysitter has her evening disturbed when the phone rings. On the other end of the line an anonymous caller asks, ‘have you checked the children lately?’ So begins a series of increasingly terrifying and threatening calls that lead to a shocking revelation.

Från IMDB:
A psychopathic killer terrorizes a babysitter, then returns seven years later to menace her again.