Born to poor parents, Becky Sharp (Reese Witherspoon) has always aspired to be a member of England's upper classes. Leaving her boarding school and best friend, Amelia (Romola Garai), behind, Becky associates herself with the Crawleys, eventually falling in love with their son, Rawdon (James Purefoy). The marriage is happy at first, but deteriorates when Rawdon's fortune dwindles. Becky is then supported by the lecherous Marquess of Steyne (Gabriel Byrne), whose motives are less than pure.