Roger Spinoza is a Parisian bookseller whose son Mathieu has committed suicide. Troubled by the realization that he never truly understood his son, Roger sets out to reconstruct his life by meeting the people who knew him. During this investigation, he encounters Valérie, his son's former lover, and becomes romantically involved with her. As he delves deeper, he is drawn into a series of strange, ambiguous, and sometimes contradictory accounts about his son and those around him. Gradually, the inquiry turns into a psychological and almost metaphysical journey: Roger begins to lose his own sense of identity, identifying with different figures and perspectives. The narrative becomes fragmented, blending reality, imagination, and subjective viewpoints, and ultimately leads to further drama and violence.