After a prologue involving the magician Cigolotti and his talking parrot, The King Stage opens with the search for a bride for Prince Deramo. The ambitious Brighella tries to prepare his cousin, Smeraldina, for an interview with the prince, in spite of her attachment to the buffoonish but charming bird catcher, Truffaldino. Similarly, the Prince’s First Minister, Tartaglia, is forcing his protesting daughter, Clarissa, to wed the Prince. Next, the elderly Pantaloon readies his daughter, Angela, for her encounter while his son, Leander, pines for Clarissa. The three girls are brought in to meet Deramo who uses and enchanted bust to ascertain whether each girl is truly in love with him or not. When the petulant Clarissa and phony Smeraldina fail to make the cut, the bust approves Deramo’s final interviewee. When the announcement of the engagement is made, Tartaglia vows revenge.
At the beginning of the second act, Tartaglia quarrels with Pantaloon over their children’s desire to wed each other. Meanwhile, Smeraldina chases after a befuddled Truffaldino. The action then shifts to the forest, with the entire court out hunting. Tartaglia uses a magic spell to move Deramo’s soul into the body of a stag and his own into Deramo’s body. Tartaglia (as Deramo) then sets the hunting party after the stag with Deramo’s soul. In the process, Tartaglia kills an old man, whose body later becomes the new vessel for Deramo when the Stag uses the same spell. Elsewhere in the forest, Truffaldino catches the magic parrot. When Tartaglia-as-Deramo returns to Angela, she senses the difference in him and no longer loves him. When Tartaglia’s lifeless body is discovered, Tartaglia-as-Deramo orders Pantaloon and Leander imprisoned.
In the last act, Deramo-as-Old-Man finds Angela and convinces her of his transformation. At the same time, Truffaldino arrives with the enchanted parrot, and Angela and Deramo plot to unmask Tartaglia. When they confront him, Tartaglia threatens to kill them both, but the parrot transforms into the Magician Durandarte. The magician switches Deramo back to his old body, placing Tartaglia in that of the Old Man. The other characters enter, and Clarissa forgives Tartaglia, who then dies. The couples are all reunited as Durandarte asks the audience’s forgiveness in his final monologue.