Though not as widely known as Hammer's popular Dracula and Frankenstein series, this is one of the studio's more stylish and intelligent projects. The tale is set in 17th century Serbia in the tiny burg of Stettel, whose residents live in fear of an encroaching plague. The frightened villagers welcome the arrival of a colorful traveling troupe dubbed "Circus of Nights," unaware that the visiting entertainers pose a far more deadly threat: the entire company is composed of shape-shifting vampires capable of transforming themselves into animals to stalk their prey. The group's leader, the most powerful monster of the bunch, has returned to the village to exact revenge on those who murdered his cousin one hundred years earlier. Less a standard Hammer monster melodrama than a surreal journey through dark fantasy (reminiscent of Jean Rollin's erotic vampire series), with an unexpected (but not entirely inappropriate) surplus of nudity and bloodletting. The film's creepy highlights include the chilling extended prologue and scenes of vampire trapeze performers transforming into bats in mid-leap.
by Cavett Binion synopsis