The Mad Ghoul may well be the definitive George Zucco horror melodrama. The star plays Dr. Alfred Morris, a distinguished scientist whose obsession with an ancient Mayan life-preserving process has tipped him over into madness. In love with young concert singer Isabel Lewis (Evelyn Ankers), Morris is extremely jealous of Isabel's boyfriend Ted Allison (David Bruce), who happens to be the doctor's lab assistant. Killing two birds with one stone, Morris uses Ted as a guinea pig for his eternal-life experiments. Ted is transformed into a mindless zombie, though he occasionally lapses back into his normal self, with no memory of his zombified state. To stay alive, Ted must maintain a fresh supply of human hearts -- and to that end, Morris programs the poor fellow to murder innocent victims and tear their hearts right out of their bodies. When Morris programs Ted to kill Isabel's new beau (Turhan Bey), he goes too far, and becomes a zombie himself. A British film critic wryly summed up The Mad Ghoul thusly: "To be a ghoul must be disconcerting enough, but to be a mad ghoul must be the height of personal embarrassment."