We have seen Marcel trace the roots of his jealousy to the fear that the lover is enjoying pleasures that he is not aware of and, indeed, that he may not be able to comprehend. He has entrusted the vigilant care of Albertine to Andrée, but now, as always, he begins to notice things. He encounters Andrée leaving his apartment and Albertine acting a bit flustered when he enters.
Once again, at the actual moment I saw nothing in all this that was not perfectly natural, at the most a little confused., but in any case unimportant. She had nearly been caught with Andrée, and had snatched a brief respite for herself by turning out all the lights, going to my room so that I should not see the disorder of her bed, and pretending to be writing a letter. But we shall see all this–the truth of which I never ascertained–later on. (V,65)
He is well-qualified to notice a change in Andrée’s personality.
Andrée’s defects had become more marked; she was no longer as pleasant a companion as when I first knew her. One noticed now, on the surface, a sort of sour uneasiness, ready to gather like a swell on the sea, merely if I happened to mention something that gave pleasure to Albertine and myself. This did not prevent Andrée from being nicer to me and like me better–and I had frequent proof of this–than more amiable people. But the slightest look of happiness on a person’s face, if it was not caused by herself, gave a shock to her nerves, as unpleasant as that given by a banging door. (V,70)