One autumn in the late 1920s, a beautiful woman called Constanza boards a train on the Italian riviera, en route to Brussels and a new marriage. With her is her young daughter Flavia, who is going to England for the education she has always wanted. An odd, almost meaningless incident interrupts their journey, and Constanza makes a seemingly abrupt and casual decision that changes the course of both their lives. Yet perhaps a pattern had already been set by Constanza's mother, the American heiress Anna, who years before had left home for a strange marriage with an Italian prince...