Animation of the popular comic book hero by Mike Mignola. When a university professor becomes possessed by the ancient twin demons of Thunder and Lightning after opening a forbidden scroll, the Bureau of Paranormal Research and Defence team of Hellboy, researcher Kate Corrigan and psychic Russell Thorne is sent to Japan to investigate the incident. There, Hellboy discovers the Sword of Storms, a cursed samurai artefact that transports him to an alternative supernatural dimension inhabited by evil spirits and grotesque monsters. He learns that the sword is the only weapon capable of defeating the demons, but it is also the key that will enable them return them to earth. As Hellboy struggles to defeat the numerous creatures he encounters before finding his way back home, his BPRD cohorts, the pyrokinetic Liz Sherman and the amphibian Abe Sapien find they, too, have their hands full with a variety of monsters that have been unleashed on earth.