At the end of World War II, Nazi officers Karl Ruprecht Kroenen and Ilsa Haupstein start an experiment to raise the forces of Hell trough Russian dark mystic Rasputin on a Scottish island, but it's interrupted by an allied commando guided by professor Trevor "Broom" Bruttenholm. He prevents killing the human-demonic half-blood, which was accidentally created and raises this "Hellboy", while rising to head of a secret C.I.A.-linked U.S. agency Bureau of Paranormal Research, which secretly studies and uses the occult, including supernatural freaks. As "father" Broom is aging, he hand-picks brilliant, sensitive Agent John Myers as new minder-companion, as regular "warrior" Agent Clay can't empathize and lacks flexibility mental. Hellboy is quite a handful, regularly spotted by worried civilians on unauthorized excursions, especially to pyro-telekinetic freak friend in a mental asylum. Johnny, Hellboy, and Clay team up on missions against paranormal threats with aquatic-bionic freak Abe Sapien. Their task proves to be daunting, as monster Sammael multiplies every time it "dies", while Rasputin and the Nazis reemerge, armed for revenge.