While examining the surroundings of Montmartre through a spyglass, the novel’s protagonist, the painter Paul Lebo, notices a fair-haired beauty in one of the windows. In trying to find her, he becomes drawn into an investigation of a terrible crime committed in the Clanjy castle.
The disappearance of an old notary, who took on the role of a righteous avenger—and with him a considerable sum of money—is only the beginning of a chain of fateful events in which all the inhabitants of the castle will become participants.