Plot

A baron down on his luck has to sell his family castle to pay off his mounting debt. After the castle is turned into a hotel, he's hired as a bellboy. But all is not lost, as he discovers he has a rich uncle; unfortunately, he's a vampire.

Baron Osvaldo Lambertenghi is forced to sell his ancestral castle; when it's converted into a hotel, he stays on as a bellboy. His mysterious uncle arrives and turns out to be a vampire. When his uncle vampirizes Osvaldo, the newly-minted blood-sucker gallops about the castle sipping from the necks of dozens of beautiful female guests.—Erewhon

To pay back taxes, Baron Oswaldo La Battengi [Renato Rascel] is forced to sell his ancestral castle to a hotel chain and take a position as the bellhop. Among the first guests to arrive is rich Uncle Rodrigo de Bonforte [Christopher Lee] from Carpathia. Oswaldo thinks his troubles are over. Hardly. Uncle turns out to be a vampire.

While Uncle goes out for a drink, Oswaldo finds his diary "Ich bin Vampyr" and has it translated by the guest Professor. He learns that vampires can be repelled by four things--garlic, a cross, a stake through the heart, and cock crow at dawn. So the next day Oswaldo makes his girlfriend Lilly [Sylvia Koscina] put garlic on her windows and paint crosses on her walls. Meanwhile, Oswaldo searches the castle for Uncle's sleeping place with the intent of driving a stake through his heart. He finds Uncle asleep under a bar (converted from a crypt) but almost gets fired from the director for leaving his post. By the time Oswaldo can sneak back into the bar, Uncle has awakened. Uncle bites Oswaldo.

When Oswaldo wakes up, he has become vampire. That's not so bad. Oswaldo gets 42 women that first night, and they all fall madly in love with him. But it's not so good either. He has no memory of his night-capades, he can't get near Lilly's house with all the garlic he made her spread around, and all the men are angry and want to kill him. Fortunately, in the end, true love between Oswaldo and Lilly drives away the curse, and Uncle convinces everyone that there are no such things as vampires.