As preparations are made for one of the younger Mitford girls to become a debutante, the family is struggling with the aftermath of the Great Depressions and have to cut corners.

Diana is seduced from her boring life as a millionaire's wife by the suave Oswald Mosley and risks everything on her relationship with him. The other girls are also considering their futures at a time of great social upheaval.

Unity persuades her parents to let her attend a school in Munich and becomes obsessed with meeting Hitler. Meanwhile, Diana is annoyed when Nancy writes a book that ridicules Mosley's fascist movement but Nancy is desperate for the money the book will bring.

Unity and Diana are furious about the release of Nancy's new book ridiculing the fascists, but Unity is thrilled with her increasing connections with Hitler and gets Diana an intro that means she can ask Hitler to support Mosley's campaign at home. The family are appalled when Unity makes hate-filled comments to the press about the "Jewish problem" but she refuses to apologise even when she's summoned home from Munich.

Diana goes to recuperate in Italy where she tries to persuade Mosley to marry her but he continues to say that it will cause too much scandal and damage his political career. Meanwhile, Unity refuses to apologise for her letter to the newspapers and insists she be allowed to return to Munich. Nancy's marriage hits rocky times when she discovers her husband in bed with her best friend.

Mosley is furious when his attempt to parade through London is stopped by protestors and the march turns into the Battle of Cable Street. Diana is more worried about her upcoming wedding while Nancy is dealing with the aftermath of discovering her husband's affair.