Anton Mordrid is a wizard sent to Earth by a being called The Monitor, to stop the evil wizard Kabal from opening the gate to Hell. Kabal needs the Philosopher's Stone and several alchemical elements to complete the spell and open the gate, unleashing his minions from the Fourth Dimension upon the Earth. Mordrid watches for signs of Kabal's presence for 150 years; as the time of their epic battle approaches, Mordrid assumes the role of a criminal psychologist, and becomes the mysterious landlord to Samantha Hunt, a research consultant to the police.
Dr. Mordrid detects a series of thefts of the elements that Kabal is seeking, and Mordrid begins to search for his nemesis. Samantha is persistent in her attempts to penetrate Mordrid's secretive life. The battle for Earth spills over into the Magic Dimension where the gate is closely guarded by other good wizards. They are no match for Kabal, who defeats all but one of them. This survivor confirms Kabal's plans for Mordrid, and Mordrid returns to Earth to prepare his defenses. When Mordrid is arrested for murder, Samantha attempts to help prove his innocence. Mordrid reveals his true nature and his mission to her, and she agrees to help him escape.
In the final showdown, Kabal and Mordrid do battle within the Cosmopolitan Museum. Using his wits and his magical power, Mordrid narrowly manages to kill Kabal, preventing the destruction of reality as we know it. His mission accomplished, Mordrid is called by The Monitor to cross over once again into the Magic Dimension and leave the Earth behind.