Martin (Charles Berling), a disillusioned 40-something philosophy professor in Paris, suffers from severe existential depression and emotional burnout. After separating from his sophisticated ex-wife Sophie (Arielle Dombasle), he stumbles into an obsessive affair with Cécilia (Sophie Guillemin), a passive 18-year-old art model who was previously involved with a deceased elderly painter. What starts as a purely physical diversion turns into an unhinged obsession for Martin when he realizes Cécilia remains emotionally unreachable and is also seeing another man, driving him to the brink of psychological and physical collapse.