Co-star Gaby André was French and spoke English with a pronounced French accent. All of her dialogue was dubbed over by an actress with a British accent.

Wyndham Goldie's (as Wyndam Goldie) final film. He died on 26th September 1957, before it was released.

Several plot elements of this low-budget film appear to have been inspired by 20th Century Fox's The Day the Earth Stood Still (1951) (1951).

Composer Robert Sharples uses a theremin in the film's opening and closing music score, creating an air of mystery and anticipation missing from the rest of the score. Composer Bernard Herrmann had previously used the theremin throughout his film score for The Day the Earth Stood Still (1951).

The film is said to have inspired the later B movie, Invasion from Inner Earth (1974) (1974).

The film was distributed in the UK by Eros Films. In 1958 it was released in the US by Distributors Corporation of America on a double bill with The Trollenberg Terror (1958) (as The Crawling Eye) (allegedly, DCA considered the alternative titles The Crawling Terror and The Crawling Horror for the second feature).

The film was first released on VHS tape in the U.S. by Englewood Video, a part of their "Science Fiction Gold" series (see cover above). Using the same cover artwork, Times Forgotten released the film on DVD, at whose website it still remains available.

On its original theatrical release, it was notably unsuccessful at the box office; it became something of a cult film due to later television syndication.

Opening credits: All characters in this film are fictitious and any similarity to any person living or dead is purely coincidental.