Young doctor Garondet is summoned by renowned Professor Orloff. At Orloff's castle, Garondet discovers that the mad scientist has created an invisible yet murderous apeman.

Julien Bouin, a former typographist, and his wife Clemence, who used to perform in a circus, hardly talk to each other in their small house, soon to be demolished. His cat Greffier being the only one he still gives affection to, he becomes the object of Clemence's anger.