Exhibits in the form of investigations are precious and rare. Even if the plot remains unresolved. Léon Monet, the name slaps. But never heard. The trace of Claude’s older brother, who was one of his first collectors, has been erased. Abnormally erased, even, as shown by the brilliant exhibition of the Luxembourg Museum devoted to the collection of the big brother of the genius of Impressionism, but also to their family stories.