In 1897, while visiting a small European country, Englishman Rudolf "Rudy" Rassendyll stops for a nap in the forest and is seen by Col. Zapt and Fritz von Tarlenheim, who are startled by his remarkable similarity to their king, Rudolf V. When the king arrives moments later, he and Rudy laugh at their resemblance, which Zapt speculates is due to a “royal scandal” several generations past. Rudolf, who is to be crowned the next day and will soon marry his cousin, Princess Flavia, invites Rudy to stay at his hunting lodge that night. True to his reputation as a wastrel and drunkard, Rudolf drinks too much at dinner, prompting Zapt to remind him of his duty. Rudolf slaps Zapt, but as soon as the colonel withdraws, Rudolf regrets his action. Before another bottle of wine is brought, Rudy falls asleep, and the king drinks alone. The next morning, when Zapt goes into the dining room, he finds Rudy asleep and the king unconscious. Zapt deduces that a drugging was arranged by Rudolf’s illegitimate half-brother Michael, Duke of Strelsau, and tells Rudy that if the coronation does not take place that day, Michael will proclaim Rudolf unfit to rule and seize the throne. Convinced that fate has brought Rudy to his country, Zapt urges him to take the king’s place at the coronation. After shaving his moustache, darkening his graying temples and donning Rudolf’s monocle, Rudy is an exact double for the king. He then accompanies Zapt and Fritz to the coronation while the comatose Rudolf is safely locked in his bedroom. Meanwhile, Michael signs a proclamation that will make him king after Rudolf fails to appear for his coronation. Although his devoted mistress, Antoinette de Mauban, begs him not to seize power, Michael refuses to be dissuaded. Unknown to Michael, Antoinette is desired by his ambitious ally, Rupert of Hentzau, who warns her that Michael can only secure his crown by marrying Flavia. Later, at the cathedral, Rupert and Michael patiently wait, sure that the coronation will not take place, then are shocked when Zapt arrives with Rudy, whom they assume is Rudolf. After Rudy is crowned, Flavia, who has not seen her cousin since childhood, is presented to him. Following the coronation, as their carriage passes cheering crowds, Flavia reminds “Rudolf” of his slights and neglect over the years, but Rudy charms her. She tells him that he has become “an entirely different person” and lets him know that she likes the change. When Rudy later speaks with Michael, he leads him to believe that he has recovered from the drugged wine and knows of his treachery. Later that night, Rudy accompanies Zapt and Fritz to the hunting lodge to change places with the king. However, when they arrive, the lodge is deserted, except for the dead body of a loyal servant, who lies next to a note reading “One king is enough for any kingdom.” Zapt surmises that Rupert, who has not been seen since the coronation, must have kidnapped Rudolf. Knowing that exposing Rupert would also expose themselves, Zapt urges Rudy to continue posing as the king. The next day, at the coronation ball, Rudy takes Flavia onto the terrace and tells her that he loves her. She also confesses her love, but wonders out loud why she fell in love him at the coronation when she did not even like him before. After Flavia responds lovingly when Rudy asks if she would care for him if he were just an ordinary man, their tryst is interrupted by Zapt, who has secretly observed them. When Rudy is alone with Zapt, he admits that his love is impossible and pleads with the colonel to find the king. Meanwhile, Rupert meets with Michael to tell him that the real king is imprisoned in the castle at Zenda. After offering Rupert money and power, Michael explains that if the imposter were killed and buried as the king, Rudolf could secretly be assassinated and Michael would legitimately assume the throne. The next morning, Rudy receives a card, addressed to his real name, asking for a secret meeting that evening and threatening Flavia if he tells anyone. Late at night, Rudy and Fritz go to the meeting place, a house that Fritz knows is owned by Annette. Rudy finds her alone in a garden cottage, where she admits that it is a trap, but tells him that she sent the note so that Michael would not be a party to murder. She also promises to arrange an escape for the king, and says that details of her plan will be revealed by a trusted servant. Just then, Rupert and his men arrive, but Rudy eludes them. The next day, Flavia is furious to learn that the king and Zapt have decided to go to the hunting lodge and assumes that Rudy has become bored with her. Rudy assures her that he is only leaving her because of duty and she senses that he is in danger. Some time later, Rupert comes to the lodge and asks to be admitted. He first offers Rudy £100,000 to leave the country, then suggests a plan whereby Rudolf will be killed, thus enabling Rudy to remain king and give Rupert all of Michael’s estates, and Annette. Zapt laughs at the suggestion, after which Rupert throws a knife at Rudy and quickly escapes. When Rupert arrives at Zenda, Annette is tending the badly wounded king, who is imprisoned in the dungeon. There Michael shows Rudolf an abdication proclamation, but the king will not sign it. Meanwhile, at the hunting lodge, Annette’s servant arrives with details of the rescue plan. Rudy and Zapt then go to the castle in the middle of the night, and Rudy swims the moat, after being given a signal from Annette. Once inside, Rudy meets Annette, who reminds him of his promise that no harm will come to Michael. As Rudy leaves Annette, Rupert hears a noise and sees light coming from Annette’s room. Thinking that her opened door is an invitation, he enters. Moments later, when her servant rattles the chain of the drawbridge, Michael awakens and hears Rupert’s laugh coming from Annette’s room. Michael opens the door just as Rupert kisses Annette. He then lunges at Rupert, but Rupert mortally wounds him with his knife and he dies in Annette’s arms, as she cries that she only did it to save him. Rupert then discovers the servant lowering the drawbridge, kills him and alerts his men. In the commotion, Rudy goes to the dungeon, but guards soon discover him. During a fight, Rudy is able to throw one of the guards into the moat through a trap door in the king’s cell, and when Rupert arrives, Rudy tells him that he has thrown the king to his death. Rupert knows Rudy is lying and draws his sword. After fighting throughout the castle, Rudy is wounded in the arm, but eventually corners Rupert, who jumps into the moat just as Zapt and his soldiers cross the drawbridge. The next day, the rescued king apologizes to Zapt for his past behavior and asks for guidance. When Rudy comes to say goodbye, Rudolf calls him his best friend and expresses sorrow that what has happened must remain secret. Zapt then tells Rudy that Flavia knows everything and wants to see him. At first Flavia is cold, but when she realizes that Rudy was not just pretending to love her, she softens. He begs her to come with him, but she refuses, saying that her duty is with the king, even though her heart will be with Rudy. A short time later, as Rudy crosses the frontier, Zapt tells Fritz that he was the finest of them all.