"For a Night of Love" ("Pour une nuit d'amour"; published in 1883); one of the most controversial novellas of its time:
"The narrative begins with a carefully accentuated picture of a serene life: that of a timid lad sequestered in a country town; this serenity is but the prelude to events of the most appalling tragedy-a tragedy which does not merely strike or wound, but positively annihilates... It is not needful to do more than say that it is one of the most repulsive productions ever published by its author, and a vivid exception to the general innocuous character of his short stories." (Edmund Gosse, 1892)
"...the poetic suggestion lurking in the tale 'Pour une nuit d'amour,' which Poe might almost have written, can only be traced with difficulty, for it is wrapped in a ghastly realism." (Ernest Alfred Vizetelly, 1904)
"It is interesting to notice from a note presumably furnished by Zola himself that the source of the plot of the psychopathic novel 'For A Night of Love' is in Casanova." (Alison M. Lederer, 1911)
More info about the Rougon-Macquart series at Wikipedia.