Émile Hazel, retired high-school classics teacher, relocates to the south of France with his wife Juliette, to what is for them a dream house, isolated and picturesque, and thus in every way the antithesis of their former city lives. On their second day of bliss, however, a knock on the door gives them a jolt, as their only neighbor, the grotesquely obese Dr. Bernardin, barges in for a cup of coffee. He stays for hours but won't converse, answering questions mostly in monosyllables. He proceeds to drop by punctually every day thereafter, with no change in attitude, forcing the Hazels to try a range of futile tactics to deter him. Even second-guessing fails: A dinner invitation to Bernardin and his wife, whom at first he steadfastly refuses to bring with him, results in a memorable evening as a bloated parody of a woman (nicknamed "the cyst" by her hosts) accompanies Bernardin and makes a meal of the chocolate sauce meant for dessert. The neighbor's solo visits continue, until finally Émile resorts to plain rudeness and shoves him violently out the door. The doctor does not return, but soon after a bout of insomnia allows Émile to rescue his neighbor from a suicide attempt, an act that binds them together in increasingly mysterious ways as the rescuer comes to realize the cruelty in his original gestureand to make amends in a way that reveals alarming, unsuspected elements of his personality.
This isn't the first time that the veneer of civilization has been stripped away to show monstrous urges beneath, but the tables turn here in a particularly eerie, chilling manner, in a combination of psychological astuteness and considerable craftsmanship.