Hellsing is named after and centered about the Holy Order of Protestant Knights, led by the current member of the bloodline of Abraham Van Helsing. The mission of Hellsing is to protect Queen and Country from the undead and other supernatural forces of evil. This organization is led by Sir Integra Fairbrook Wingates Hellsing, who inherited the leadership of Hellsing as a child after the death of her father. She is protected by the faithful Hellsing family butler and former Hellsing "trashman," Walter C. Dornez, and Alucard, a powerful vampire that was captured by the family a hundred years ago and serves as the organization's current "trashman." These formidable guardians are joined early on in the storyline by former police officer Seras Victoria, whom Alucard turned into a vampire.
As the scale and frequency of incidents involving the undead escalate in England and all around the world, Sir Integra discovers that the remnants of a Nazi group called Millennium still exist and are intent on reviving the Third Reich with an army of immortal vampires. The operatives of Millennium, Hellsing, and the Vatican Chapter XIII Iscariot clash in an apocalyptic three-sided war in London, and Millennium reveals its true objective: to destroy the vampire Alucard and end a feud begun in the last World War.