Transylvania, in the 1800's, at Count Dracula (Dan Meaden)'s castle, the Count is attacked by a man we can't see, helped by Igor (Skip Martin), a dwarf man. He's put garlic in his mouth. Merlin (Ringo Starr) laments and cries out that he should have helped him, as Dracula was the Kind of the Netherworld. Countess Dracula (Lorna Wilde) is sleeping and heavily pregnant with Dracula's child; Merlin will educate this child to become the new kind of the Netherworld when it's born, but it'll take long for the baby to be born.
100 years afterwards, a funeral car carries a coffin and crosses the English Channel. It's the rock years, and a couple is making out in a messy bedroom. She gets money from the chauffeur (David Bailie), who leaves immediately. She has been waiting for the person in the coffin to appear; she is happy, but Bill (John Coleclough) has already died bitten by the vampire. She enjoys being bitten by Dracula's son.
At Merlin's, he learns that the vampire is on his way. Baron Frankenstein, usually called the Baron (Freddie Jones) gives the news to Merlin. He is t old that the crowning must happen in the next 72 hours. Count Downe (Harry Nilsson) also visits Merlin for the occasion - he's not been studying music recently. Down goes to Piccadilly, Hyde Parks, Leicester Square, and wonders at all the shiny placards. He goes to Tramp, 40 Jermyn Street, a music pub, where a woman (Rachelle Miller) immediately offers him a cigarette, which he rejects. He goes to the stage to play and sing. Later that night, Downe stalks a woman who's wearing a bouquet of flowers and defends her from the attack of a monster (Morris Bush). Sher offers herself to be bitten by Downe.
At a museum, the exhibition is about death and torture. An old man in a wheelchair follows Downe. Van Helsing (Dennis Price) is the administrator of the museum. Downe's room has been prepared especially for his rest and coronation day. He plays the piano and sings there. Downe chooses his coffin. Merlin worries that Downe didn't become a vampire the normal way, as he was born. The housekeeper (Shakira Baksh-Caine) hypnotizes the Baron by means of the eyes of a cat.
In his casket, Downe dreams of his father's death and of him as a child, and how a woman offered her neck to him but she was wearing a cross which burnt him in his hand and let a scar for all eternity. In the morning, he closes the window - light seems to disturb him, but not kill him. Downe will miss the human world and emotions, and he tells so to his valet and chauffeur. He visits Merlin in the day, in a limousine with tainted windows. Merlin tells him that his mother was human, and that he's inherited qualities from her as well. However, only Downe can take that decision.
At Harley Street, Baron Frankenstein will perform an operation in his brain so that he can become king, and immortal in human life. But they don't have a lot of time. A machine is needed for the operation, which must take place at the following day during the night. The Baron calls for Igor and prepares a plan: to kill Downe during his operation. However, Merlin hears the plan from a magic mirror. The Baron wants to become the king himself.
Downe sees his future throne. Van Helsing's assistant, Amber (Suzanna Leigh) happens to be the woman who had the crucifix as a necklace. She is preparing the coronation. They have dinner together. Downe sings a nonsensical song. Amber and Downe are in a bed tother, but she has tattooed a crucifix in her chest [it's more like a non-suntanned part of her skin]. He beomes a cartoon bat. Downe opens the coffin. Van Helsing has tea with Downe and tells him that love would only bring him total sadness. Van Helsing can perform the operation himself. He dreams of Van Helsing taking away pieces of viscera from him.
The Baron complains to Merlin about not having the machine. Merlin tells him that Downe has decided in favour of Van Helsing implanting on him human love. The Baron goes frantic. At the Thornton Medical Institute, Igor and Van Helsing pretend to be staff and steal the radioactive thing they need. The police run after them although they have run in an ambulance; finally, they let them go.
The chauffeur and the Baron talk. Merlin says that the former has always been a loyal servant. The Baron speaks to some ghosts about humanizing Downe. The valet interrupts Amber and Downe, as the latter needs to talk to the council. Guests arrive and want to have a piece of Downe.
The Monster attacks Amber and the chauffeur. Merlin sends the cat to wake up the valet as the allies of the Baron attack. Nilsson's renown song Without You while Amber and Downe are holding hands on a bed and the operation is performed.
Downe tells to all the crowd that he doesn't want the crown; people get mad at him and the gobblins try to attack. The valet discloses a cross in the ceiling through which sun enters, killing everybody, except for the valet and Downe. Merlin finally faces the Baron, who wants to become the new Overlord. Merlin makes the Baron disappear with billiards balls.
Downe joins Amber in the daylight. They hold hands and leave together, in love.
The End over the shining sun. Suddenly, the caption Or is it? appears over-imposed, and then the face of Merlin appears.