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.

Mónica has just died in a traffic accident. Along with her was another man. Pedro Bernáldez, painter and lover of Mónica, was so in love with her that he came to change his painting style for the one indicated by his lover. Now that Mónica has died, Pedro will investigate what relationship the deceased had with each other and begins to discover many things.