Off the coast of northern Germany lies the island of Growerth, a place where the supernatural is not a myth but a mundane reality. The island is ruled by Viscount Gerhard von Waldstein, a vampire who is perhaps the least vampire-like member of his kind. His body is composed entirely of liquid blood, and his gentle, eccentric, and merciful nature has turned Waldstein Castle into a sanctuary for all manner of non-humans seeking refuge from a world that fears them. Within the castle walls live a chaotic community of fellow vampires, witches, werewolves, and even eldritch abominations. At the heart of this household are the Viscounts twin children, Relic and Ferret, who navigate their immortal adolescence alongside their human childhood friends, the Dietrich siblings, Michael and Hilda.

Life on Growerth is far from peaceful. In the nearby city of Rukram, the trash-talking dhampir mayor, Watt Stalf, harbors a deep-seated grudge against the Viscount. As a half-breed, Watts frustrations with the vampire world manifest in violent outbursts and a hair-trigger temper, making him a volatile and unpredictable force on the island. The chaos deepens with the arrival of other singular individuals, such as a young woman with a disturbing appetite for vampire flesh known as an Eater, and a shapeshifter burdened with a complex about his monstrous true form.

The narrative sprawls outward to encompass a much larger conflict involving the Organization, a shadowy and massive collective of vampires numbering in the thousands. Formed to protect their kind from human persecution, the Organization is a byzantine bureaucracy of powerful eccentrics led by an elite cadre of executives known as the Rainbow, each bearing a color-based title like the Crimson Blood and the Blue Blood River. Despite their power, the Organizations true goals are often hilariously unclear, with its own members frequently unaware of the larger plot. Their activities draw in operatives from across the globe, including professional vampire hunters and other Eaterschanneling the powers of consumed vampires, such as the vengeful Rudy Vanders and the formidable Theresia Riefenstahl.

Several major narrative arcs drive the series forward. A central thread involves the tragic history of a vampire named Theodosius, who was turned through horrific experimentation as a young boy, leading to a devastating rampage that connects the fates of Rudy, Watt, and the Viscount. Another significant arc focuses on the political and physical confrontations between the Viscounts free-wheeling household and the rigid, scheming hierarchies of the Organization, often dragging neutral parties and the human residents of Rukram into the crossfire. Power dynamics constantly shift, as weaker characters like the half-breed Watt struggle against their limitations, only to gain immense power through unexpected means, challenging the established order of the vampire world.