King Rudolf V of Ruritania (Stewart Granger) is suddenly abducted just days before his coronation is to take place. The king's evil brother, Prince Rupert (James Mason), is behind the kidnapping plot, and plans to seize the throne for himself. As the king's supporters try to find him, they stumble upon Rudolf Rassendyl (also Granger), an identical distant cousin who can pose as the betrayed ruler. The plan works well until the king's fiancée, Princess Flavia (Deborah Kerr), suspects foul play.