After the success of Halloween (1978) director Fred Walton decided to expand a short film into a feature one, which resulted in cult classic When a Stranger Calls (1979). First 20 minutes of the latter is a shot-for-shot remake of this short film.
This short film was initially unavailable to the public for decades, to the point where many fans assumed the opening 20 minutes of When a Stranger Calls (1979) was this short film, with the rest tacked on later. This was proven not to be the case when it turned up as a special feature on Second Sight UK's Blu-ray release of the original film, and later on Scream Factory's Blu-ray of When A Stranger Calls Back (1993), having been included due to fan demand.