MURDERS IN THE RUE MORGUE
In 1845, at a Parisan carnival, Pierre Dupin and his fiancee Camille enter the sideshow tent of "Erik the Ape". Inside, the ape's owner, Dr. Mirakle (Lugosi), gives a brief lecture on evolution. As Mirakle concludes his oration, he draws the curtain of Erik's cage and announces dramatically, "Behold-the first man." Mirakle answers shouts of "Heresy" from the audience with animated talk of his "great experiment." "I shall prove your kinship with the ape", he claims above his listeners protests. "Erik's blood shall be mixed with the blood of man!". After the show, Pierre and Camille approach Erik's cage to get a closer look. Suddenly, Erik snatches the bonnet from Camille's head and then nearly throttles Pierre when the young man tries to retrieve it. The ape is taken with her - as is Dr. Mirakle, who watches with an unhealthy curiosity.
Later that night, Mirakle and Erik follow Camille to her residence. They move on, however, and Mirakle soon spies a streetwalker in near-hysterics after witnessing two men kill each other over her in a deadly streetfight. Mirackle first cajoles, then forces, the girl to enter his carriage, upon which she screams and they drive off. At a secret laboratory, Mirakle injects her with a sample of Erik's blood. When she dies, Mirakle blames his failure on her own contaminated blood. "Your blood is rotton, black as your sins", he rails to the corpse.
The girl's body is fished out of the river (the third such victim) and brought to the morgue. Pierre Dupin, a medical student, arrives at the morgue to procure "supplies". When he examines the fresh body, he notices "the same marks" on the corpse's arm as on those of the previous two victims. Pierre bribes the attendent for a blood sample, in which he finds "the same foreign substance in the blood of each victim....something introduced into the bloodstream to cause their death.
Camille receives a new bonnet from Dr. Mirakle, who asks her to visit him that night. Upon learning of this, Pierre goes instead of her and recieves a curt dismissal from the disappointed doctor. His suspicions aroused, Pierre follows Mirakle and watches him enter an abandoned house. That night, Mirakle goes to Camille's apartment, but the frightened girl shuts the door in his leering face. Not to be denied, Mirakle sends Erik into the house after her. Meanwhile, Pierre discovers that the foreign substance in the woman's blood is the blood of a gorilla. Suddenly concerned for Camille, he races off towards her apartment.
Erik climbs up the side of the building and enters Camille's room, upon which the girl screams and faints. Her cry awakens her mother, who rushes into the room only to confront the enraged Erik. Pierre arrives as the mother's screams and Erik's howls arouse the building's other residents. With help, Pierre breaks down the door. Inside they find Camille gone and the body of her mother stuffed up the chimney. Dupin tells the prefect of Police about Mirakle and his ape, but the police think him insane. Gorilla hair clutched in the corpse's hand finally convinces them otherwise, and Pierre leads the gendarmes to Mirakle's house. As the Police try to break in, Mirakle lets Erik out of his cage. When Mirakle approaches the unconcious Camille, however, Erik goes ape and strangles his master (presumabley because the simian has fallen in love with her - though this is only hinted at and never made clear). The gendarmes shoot Mirakle's servant, Janos, and break in, but Erik has carried Camille to the roof.
Pierre follows as the gorilla races across the rooftops of Paris. Finally, Pierre corners Erik and shoots him with a gendarme's borrowed pistol. As Erik rolls off the roof into the rushing river below, Pierre and Camille embrace. At the morgue, the dour attendent receives the body of Dr. Mirakle.