Hammer's double threat, Maltese twins Mary and Madeleine Collinson, first appeared on the screen in 1972 as the naughty and nice sisters in Twins of Evil (aka Daughters of Darkness). The girls were no stranger to the spotlight, however, having posed for Playboy as the first twin playmates in 1970. Hammer Films saw dollar signs in their eyes and pursued the twins for their third film in the Karnstein Trilogy. The popularity of the Twins earned them a big reputation; they even appeared on Johnny Carson's The Tonight Show. Though the girls were inseparable friends, their acting career was not meant to be as a team. "There is no hope of a steady succession of parts for the pair if we stay together," Madeleine expressed in 1971. The twins amicably went their separate ways after a short series of small roles, but the highlight of their career was with Hammer.
After the first two films in the trilogy, The Vampire Lovers and Lust for a Vampire, Twins of Evil feels quite tame for Hammer. There is a drastic decrease in nudity and the focus of the vampire's 'affections' are for men not women. I suppose the titillation was in the novelty of twins and less on lesbian vampires. Don't get me wrong though, there are still enough naked breasts to please the sleaze in all of you. Also new for the film was the blurring of good and evil. Hammer's storylines always made clear distinctions between the two, but the twins stir up a little double trouble action.