It is reported that MGM forced Dan Curtis to cut over 35 minutes from the completed film, and gave him only 24 hours to do the job. So the film, which was meant to be approximately 129 minutes, was shortened about 94 minutes, which according to some caused the film to lose its coherence. Much of the excised footage was recovered in 1999, but unfortunately, without sound.
This was originally intended to to be a sequel to House of Dark Shadows (1970), and was to star Barnabas Collins (Jonathan Frid). Frid however turned down the role as he feared being typecast as Barnabas, so "Dark Shadows" creators Dan Curtis and Sam Hall made a new story which starred Quentin Collins and was based on the "Parallel Time" saga of the show (an alternate version of the story).
Filmed on the grounds of the Gothic estate Lyndhurst on the Hudson River in New York State in the same location where 'House of Dark Shadows' was filmed the previous year. In contrast to 'House of Dark Shadows' which had several location scenes filmed in nearby Tarrytown as well as Connecticut, this film takes place entirely on the grounds of Lyndhurst as the backdrop for the Collingwood mansion.
A prologue was scripted but never filmed that involved a hippie that sneaks into Collinwood on a rainy night only to be killed by Angelique and Gerard. The role of the hippie was intended to be played by either Keith Prentice or Michael Stroka.