Monsieur Cousin, a lonely Parisian statistician, shares his small apartment with a python named Gros-Câlin, seeking warmth and companionship. Infatuated with his coworker, Mlle Dreyfus, he awkwardly tries to win her affection, misinterpreting social cues and struggling with human connection. His eccentric attachment to the snake alienates him further, as his longing for intimacy blurs the line between reality and fantasy. Despite seeking advice and making misguided attempts at love, he remains isolated. The film follows his tragicomic struggle, ending ambiguously as he grapples with his unfulfilled need for human warmth.