Gillian Hills was a last-minute replacement for Marianne Faithfull, who was re-cast due to insurance reasons.
Although this movie was completed in 1971, it sat on the shelf for over a year and was finally released on a double bill with the psycho movie, Tower of Evil (1972).
Robert Hardy replaced Eric Porter, who withdrew from this movie to film Hands of the Ripper (1971), which was made simultaneously.
The role of Baron Zorn was originally offered to Paul Scofield and James Mason, both of whom turned it down.