The script is expanded from a sequence originally written as part of Dario Argento's first film, Uccello dalle piume di cristallo, L' (1969), but never filmed due to time constraints
This originally aired as the second episode of Italian director Dario Argento's failed television series "La porta sul buio" (English Translation: "Door into Darkness"). Other episodes in the series are Vicino di casa, Il (1973) (TV), Testimone oculare (1973) (TV), and Bambola, La (1973) (TV).
The original film elements to this (along with the other three episodes of the series) no longer exist according to the MYA Communications DVD release. Because of this they were forced to transfer from the original RAI TV video masters.