The Mad Ghoul

Dr. Alfred Morris is interested in the effects of an ancient nerve gas that the Maya used during ritual sacrifices to appease their gods. He takes under his wing a medical student Ted Ellison, whom he asks to help him in experiments on the use of gas on animals. Together they succeed in experiments to revive Morris Choco's dead monkey, which had previously been exposed to gas and died, with the help of liquid extracted from the heart of another creature. Ted is constantly thinking about his girlfriend Isabelle Lewis, who is also secretly in love with Morris.

On the night of the first joint experiment, Ted brings Isabel to Morris' house, where he notices her discomfort about her relationship with Ted. He talks to Isabelle and hints that she needs a man more involved in her love of music, meaning himself. Isabelle is afraid of hurting Ted by telling him she wants to break off the engagement, but Morris promises to take care of it himself. Isabelle does not know that Morris plans to expose Ted to the deadly Maya gas and, in fact, turn him into a brainless ghoul dependent on liquid extracted from the hearts of people who have just died. As a result, Ted and Morris are forced to rob graves in the cities where Isabel performs as part of her tour. Morris tries to get Ted to come home, but he tends to be with Isabelle when he is not unconscious. When Ted once again becomes a ghoul, Morris uses him to try to kill the only person Isabelle really loves–Eric Iverson, her partner and pianist. Although this attempt was unsuccessful, Ted can get another heart and save his life.

Eventually, the police, aided by a top-notch reporter McClure, realize that the mysterious murders are taking place on the route that Isabel's tour takes. McClure tries to set a trap in Scranton, the last city of the tour, pretending to be a recently deceased person and waiting for a ghoul in a coffin. He almost manages to grab Ted and Morris, who come to the cemetery for another heart. However, Morris distracts McClure, after which Ted kills him.

When Isabel returns home, the police find out from her why the murders were committed in the same cities in which she performed. She claims she doesn't know anything about it, but understands that Ted and Dr. Morris are the only people connected to her who also know how to perform a cardioectomy. Later, she performs for a home audience, and Morris, in a last-ditch attempt to get Isabel, sends Ted to kill first Eric, then himself. However, Ted, before becoming a ghoul, writes a letter to Isabel in which he explains what is happening to him and who committed the murders. In addition, right before the transformation, he exposes Morris to gas, after which he leaves to fulfill the doctor's last will. Ted goes on stage to Isabel, and the detectives kill him. Eric reads Isabelle the letter that Ted gave him. Now Isabelle and Eric know that Ted always wanted the best for them, and Morris was behind all the problems.

Meanwhile, Morris, who has been deprived of almost all his vitality by the gas, almost succeeds in getting fluid from his heart, but falls dead at the excavated grave. At the end of the film, the words said earlier by Ted to Morris are repeated: "It's over, Doctor. Now there's nothing left but you, me and... death!"