The Gist: A town plagued by disease is visited by a circus which happens to be run by vampires.
Clarification: A hammer horror film so it obviously takes place in the 19th century somewhere in Austria. Anyway a town as always in these films was being plagued by vampires, the townspeople find out and they kill him but not before he puts a curse on the town. A few years later many of the towns people are dying and the town is cut off from the rest of the world do to the plague but somehow a traveling circus comes in to entertain the towns folk. Once this happens people start to die and children go missing (the vampires in these films had a thing for attacking kids).
As per usual the towns people eventually figure it out and the vampires die in a firey mess (there are quite a few plot twists in the film but I won't spoil them all).
Selling Point/Female Vampire Factor: You get one real female vamp in the film (at least that fangs out anyway). As part of the circus there is a pair of acrobat twins vampires. The female twin Helga is played by Lalla Ward