Herve Joncour is a married silkworm smuggler in 19th century France. He travels to Japan to collect his clandestine cargo after his original shipment was destroyed. While in Japan, he spots a beautiful Japanese woman who is the concubine of a local baron. He immediately becomes obsessed. Without speaking the same language, they communicate through letters until war intervenes. Their unrequited love persists however, and Herve's wife Helene begins to suspect something is going on with her husband.