It is the second film in the Karnstein Trilogy, loosely based on the 1872 Sheridan Le Fanu novella Carmilla.

The three films do not form a chronological development, but use the Karnstein family as the source of the vampiric threat and were somewhat daring for the time in explicitly depicting lesbian themes.

Novelist Richard LeStrange has come to the village to get background for his books about witches, vampires and black magic.

However, dance teacher Janet Playfair notifies both the police and Mr Pelley, all of whom arrive to investigate.

The Karnsteins manage to kill the policeman who has just discovered Susan's body in the bottom of a well, but Mr Pelley arrives with a writ of exhumation and a pathologist to investigate his daughter's death.

He says it was based on an original script he wrote for Mario Bava about a girls school which had a serial killer.

[7] Bates had earlier appeared in Taste the Blood of Dracula with Madeline Smith, who starred in The Vampire Lovers.

The song "Strange Love" was recorded for the film by Tracy, a teen singer from Wembley, and released as a 7-inch single, produced by Bob Barratt.

The Monthly Film Bulletin wrote: "Despite its exploitative title, Hammer's second excursion into the territory of Le Fanu's Carmilla is – like The Vampire Lovers – reasonably in keeping with the spirit of the original ... Yutte Stensgaard's Mircalla effectively exudes an aura of utterly sensual evil, and Ralph Bates is excellent as the occult scholar who becomes infatuated with her, while Le Fanu's claustrophobic girls' dormitory world is nicely evoked in images ... that build up an atmosphere of properly cloying intensity; and one long, particularly audacious tracking shot down the garden to the lake (in which the camera becomes Mircalla stalking and embracing her victim) communicates just the right feeling of narcissism and ghostly physicality. ...

"[9] Bruce G. Hallenbeck asserts that "there is much to recommend" the movie, noting that a Gothic atmosphere is "ably evoked", and adding, "I think it was a very good script".