The cast members were paid $1000 each plus a share of the profits to be paid out later. However, American-International never paid out any of these shares.
The tuba music during the opening credits is the "Dies Irae" section of Hector Berlioz' "Symphony Fantastique." A different version of the same piece was later used during the opening credits of Stanley Kubrick's The Shining (1980).
In an interview included in the Extras on the Mystery Science Theater 3000 (1988)-riffed disc, Peggy Webber said that director Alex Nicol wanted her to fall down a flight of stairs at one point. It was then she told him that she was three months pregnant and that it would be unsafe.
The death-mask on Marian's tombstone is a reproduction of the famous "l'Inconnue de la Seine," reputed to be the face of a young French suicide who, like the deceased wife in the film, died in the water.