On the eve of the coronation of King Rudolf of Ruritania, his brother, Prince Michael, has him drugged. In a desperate attempt not to give Michael the excuse to claim the throne, Colonel Sapt and Fritz von Tarlenheim, attendants of the King, persuade his distant cousin Rudolf Rassendyll, an English visitor, to impersonate the King at the coronation.

The unconscious king is abducted and imprisoned in a castle in the small town of Zenda. There are complications, plots, and counter-plots, among them the schemes of Michael's mistress, Antoinette de Mauban, and those of his dashing but villainous henchman Count Rupert of Hentzau.

Rassendyll falls in love with Princess Flavia, the King's betrothed, but cannot tell her the truth. He determines to rescue the king and leads an attempt to enter the castle of Zenda. The King is rescued and is restored to his throne, but the lovers, in duty bound, must part forever.