A young man visits his fiancée in a rustic French countryside cottage where Georges Zucco's oddball scientist father (Georges Zucco) lives. He then encounters Noel (J. Carrol Naish), the mysterious assistant of Dr. Renault's, who has a captivating allure for the driver's daughter. After a while, Noel's true identity is revealed: he was an ape that was transformed into a man. Dr. Renault's Secret is a 1942 thriller film written by William Bruckner and Robert Metzler. It is loosely based on the 1911 novel Balaoo by Gaston Leroux.