Hervé Joncour travels the world buying silkworm eggs and eventually travels as far as Japan. He buys eggs from Hara Kei, a French-speaking nobleman. Joncour falls in love with his mistress. During his second visit to Japan, Joncour learns about the aviary of exotic birds that Hara Kei has built; he leaves a glove for Hara Kei's mistress to find in a pile of clothes. Hara Kei's mistress gives him a love note written in Japanese that says, "Come back, or I shall die."

During Joncour's third visit to Japan, Hara Kei's mistress releases the birds from the aviary. Joncour and Hara Kei's mistress have sex by proxy. Hara Kei conducts the silkworm egg transaction via an associate and does not say goodbye when Joncour leaves. When it is time for Joncour to make a fourth trip to Japan, war has broken out. He finds Hara Kei's village burned to the ground. A young boy appears and gives him the glove that he had dropped on the pile of Hara Kei's mistress's clothes. He follows the boy to the place where the refugees from Hara Kei's village are camping.

Hara Kei denies Joncour welcome but Joncour refuses to leave. The next morning, Joncour sees the body of the boy hanging from a tree; Hara Kei has executed him for carrying the glove to Joncour and bringing him back to the village. Joncour hastily procures a supply of eggs but leaves far too late in the season to transport them to France. The silk mills sit idle that year.

One day, he receives a letter written in Japanese. He takes it to Madame Blanche. It is an erotic love letter from a woman to her beloved master. Madame Blanche gives him some of her trademark blue flowers. Joncour retires from the silkworm egg business; he and Hélène have three daughters. Baldabiou leaves Lavilledieu suddenly and is not heard from again. Hélène dies of a fever several years later. On a visit to her grave, Joncour sees Madame Blanche's blue flowers there. He visits her and learns that his wife is the author of the letter.