Trivia

Shot in 1965, not released in the US until 1971.

The monster mask used in the film was originally made for A Feasibility Study (1964).

Billed as "2nd Thriller Chiller" on the poster on a double bill with "Blood Suckers", none of the unknown cast's names are mentioned as opposed to 1st feature's stars Patrick Macnee and Peter Cushing, whose names are there, selling both movies.