Michael Pitt stars as Herve Joncour, a Frenchman who lives in a small town that has hit hard times. A local silkworm magnate (Alfred Molina) stumbles upon a solution for his towns troubles, and enlists Herve to travel to a hidden corner of Japan in order to smuggle back a boundless supply of rare silkworms.
Travelling in disguise so that he will not be exposed, Herve succeeds in his mission. Upon returning home, he reunites with his beautiful, supportive wife, Helene (Keira Knightley). While Herve and Helene have a loving relationship, their inability to produce a child creates an undercurrent of distance between them. This is compounded when Herve meets a beautiful concubine (Sei Ashina) during one of his subsequent journeys, sparking a passionate encounter that will haunt him for the rest of his life.