Beneath the quaint spender of a San Francisco mansion there lurks an unspeakable evil, Dr. Jekyll's Dungeon of death. There, deep in the bowels of his underground lab, Jekyll conducts a bloody experiment with human life in desperate attempts to recreate his great grandfather's secret serum. Assisted by his lobotomized sister and a giant black cripple, Jekyll searches the dark streets of night for unsuspecting victims who are to become his tortured guinea pigs. Failure brings desperation as Jekyll holds a professor's daughter hostage to get him to cooperate with his mad plan. A final confrontation between good and evil brings about a blood-soaked climax that will shock and astound you!