Count Mitterhaus [Robert Tayman] was a vampire, preying on the children of the town of Stetl. With the death of one more child, the people became sufficiently enraged that they stormed the Count's castle and drove a stake through his heart. With his dying breath, Mitterhaus vowed, "Your children will die to give me back my life." Seven villagers went in, four came out -- Professor Albert Mueller (whose wife Anna had become the Count's willing consort), the Burgermeister, Dr Kersh, and Herr Hauser. Just as the castle is consumed in flames, the Count whispers to Anna, "Tell Emil. He will know what to do."Fifteen years later: The town of Stetl is dying, literally. A plague is slowly killing the people, although some believe it is the Count's curse at work. At any rate, neighboring villages, afraid that the plague/curse may spread, have placed roadblocks around Stetl, and they vow to shoot anyone attempting to leave or enter the town. Dr Kersh [Richard Owens] is among those who believes it to be a disease not a curse, and he plans to sneak out of the town and bring back knowledge and medicines from the city. With his son Anton [John Moulder-Brown] acting as a decoy, Dr Kersh manages to get away. Before his father leaves, Anton reminds him to find his girlfriend Dora Mueller [Lynne Frederick], the daughter of Professor Mueller [Laurence Payne] and tell her not to come back. Unbeknown to them, Dora is already planning to sneak through the roadblocks in an attempt to get back to her father and to Anton.Somehow, the Circus of Night manages to make it through the roadblocks. Tricks, performances, dancers, aerialists, wild animals -- the people of Stetl are, at least, to be entertained in their misery. But this is no ordinary circus. Serena [Serena], for example, dances totally nude, except for the tiger stripes on her body, aerialist twins Helga [Lalla Ward] and Heinrich [Robin Sachs] turn into owls as they soar through the air, and when the panther jumps up, he comes down in the body of Emil [Anthony Corlan], who seems smitten with the Burgermeister's daughter Rosa [Christina Paul], and she with him. Emil is a vampire, really Count Mitterhaus's cousin. The ring mistress, known simply as the Gypsy woman, is really Anna Mueller [Domini Blythe], and the twins are her children with the Count. Their purpose in Stetl is not to entertain, but to kill.First to suffer the consequences is the Burgermeister [Thorley Walters] when he is invited to make a special trip through the "Mirror of Life." At first, he is overcome with laughter at the silly distortions in the various mirrors. In the last mirror, however, he sees himself being bitten by the Count, who speaks to him, reminding him of his curse. Schilt [John Bown] and his family are among those who believe that the Count's curse is coming true. Schilt bribes Michael [Skip Martin], the circus dwarf, to lead him, his wife, and his mother out of town. Michael is happy to comply but leaves them stranded just beyond the roadblocks, where they are torn up by the panther. Next to be invited through the Mirror of Life are the Hausers, Jon [Roderick Shaw] and Gustav [Barnaby Shaw]. In the final mirror, they see the twins, Heinrich and Helga, who take them through. The next morning, their bodies are found lying on the ground, drained of blood, with holes in their necks. The Burgermeister, afraid that his daughter will be next, orders that all the circus animals be killed. Herr Hauser [Robin Hunter] shoots the monkey and the tiger, but just as the Burgermeister is about to shoot the panther, he has a heart attack, and Emil disappears. Next is Rosa's turn. Emil leads her to the crypt where the Count's body is being kept. There, Emil bites Rosa and allows her blood to spill on the Count. Emil vows that tonight Professor Mueller's daughter Dora will die, and the Count will live. During the next circus performance, Dora is invited through the Mirror of Life. Anton follows, just in time to see her go through the mirror. Heinrich prepares to bite her neck but is thwarted by the cross around it, and she is cast out of the mirror.Dr Kersh returns to Stetl with the information that the plague is actually a virulent strain of rabies caused by bats. He brings medicines, but he also brings the news that there are vampires in the land and that, in each case where people have been reported killed by vampires, the Circus of Night has stayed for a day or two. It appears that Stetl must rid itself of two plagues, not just one.Following her brush with the vampires, Dora has locked herself in the living quarters of the school where her father teaches. But that doesn't thwart the vampires. Emil gets through an open window on the second floor, changes himself into the panther, and attacks the students, killing every last one. Meanwhile, Heinrich, Helga, and the Gypsy find Dora. The Gypsy removes the cross from Dora's neck, and Heinrich and Helga draw in for the kill. Dora runs to the school chapel where she knocks over a cross that impales Helga and, by twin empathy, the gaping hole also appears in Heinrich's chest. Emil and the Gypsy escape, but the Strongman [David Prowse] breaks into Dora's house and takes her and Gerta Hauser [Elizabeth Seal] to the crypt. Hauser, Mueller, Dr Kersh, and Anton form a brigade of vampire hunters and they storm the circus, killing the Strongman. Hauser sets the Mirrors of Life on fire, but he becomes trapped in the flames and burns to death. The vampire hunters figure that the Count is probably in the crypt, so they head there.Meanwhile, Emil has just finished feasting on Gerta Hauser and turns his attentions to Dora. As he leans forward for the bite, the Gypsy (who has been holding Dora) aka Anna suddenly pushes her daughter to the side, and Emil bites Anna instead. Anton attempts to chase off Emil with a crucifix, but a bat knocks it out of his hand. Suddenly, the other vampire hunters break into the crypt and tussle with Emil. Emil kills off a number of them, but Mueller manages to pull the stake out of the Count's body and uses it to stake Emil. With the stake removed from his chest, the Count wakes up. He goes after Dora, but Anton beheads him with a crossbow. Only Dora, Anton, and Dr Kersh manage to survive the carnage. [Original Synopsis by bj_kuehl]
Output: Question: Who is the daughter of Professor Mueller?, Answer: Dora