Set in historical Styria, identical twin sisters Maria and Frieda Gelhorn move from Venice to Karnstein in Central Europe to live with their uncle Gustav Weil after becoming recently orphaned.

Count Karnstein, who enjoys the Emperor's favour and thus remains untouched by the Brotherhood, is indeed wicked and interested in Satanism and black magic.

Trying to emulate his evil ancestors, he murders a girl as a human sacrifice, calling forth the vampiress Countess Mircalla Karnstein from her grave.

While the Brotherhood debates the vampire woman's fate, the Count and his servants kidnap Maria and exchange her for Frieda in the jail cell.

Weil now listens to Anton's advice on hunting vampires, and the two men lead the Brotherhood and the villagers to Castle Karnstein to destroy the Count.

The scene is out of place as their uncle is busy burning the other sister; somehow he teleports back home and the evil twin gives him a show.

The Monthly Film Bulletin wrote: "The repressive austerity of the Puritans' life style – the bare oak walls of the meeting house and Weil's home, Cushing's ascetic features and clipped delivery – provides a running contrast to the high Gothic of Don Mingaye's lavish baronial set for Karnstein Castle, replete with mists, shadows and colour filter effects.

...Where Tudor Gates' previous Le Fanu adaptations (The Vampire Lovers, Lust for a Vampire) provided only the most anaemic opposition to their heroines' atrocities, in Twins of Evil the crusader role is interestingly transferred to the strong but morally equivocal Puritans, and as a result the film provides a study in opposites which never resolves simplistically into Good and Evil.

The reincarnation of Countess Mircalla, an ectoplasmic shape rising from the sarcophagus and floating in hooded silence towards the terrified Karnstein, is a tour de force.

And though Twins of Evil has its share of the usual Hammer deficiencies – insipid juveniles and some over-familiar Pinewood locations – it is easily the best of their vampire films for some time.

"[6] In Cinefantastique Robert L. Jerome observed: "The film is done with Hammer's obvious care for details and a sobriety which creates the proper mood of unexpected evil in attractive, tranquil surroundings.