The play opens with a puja to Ganesha, as the Bhagavata asks that Ganesha bless the performance that he and the company are about to put on. Then he places the audience in the setting of the play, Dharmapura, and begins to introduce the central characters. The first is Devadatta, the son of a Brahmin who outshines the other pundits and poets of the kingdom. The second is Kapila, the son of the iron-smith who is skilled at physical feats of strength. The two are the closest of friends.
As the Bhagavata sets up the story, there is a scream of terror offstage. An actor runs onstage screaming that he has seen a creature with a horse’s head, a man’s body, and the voice of a human. The Bhagavata doesn’t believe him, and even when the creature (Hayavadana) enters, the Bhagavata thinks it is a mask and attempts to pull off Hayavadana’s head. Upon realizing it’s his real head, the Bhagavata listens as Hayavadana explains his origin: he is the son of a princess and a celestial being in horse form, and he is desperate to become a full man. The Bhagavata suggests he go to the temple of Kali, as she grants anything anyone asks for. Hayavadana sets out for the temple, hopeful that Kali will be able to change his head to a human head.
Recovering from the interruption, the Bhagavata returns to the play. He begins to sing, explaining that the two heroes fell in love with a girl and forgot themselves. Meanwhile, a female chorus sings in the background about the nature of love. Devadatta and Kapila enter. Devadatta explains his love for Padmini, explaining that he would sacrifice his arms and his head if he could marry her. Kapila at first makes fun of Devadatta but then sees how much his friend is affected by Padmini. He agrees to find out her name and where she lives.
Kapila goes to the street where Padmini lives and begins to knock on the doors. When Padmini opens the door to her home, Kapila is immediately love-struck. Padmini asks him what he wants, outwitting him as he tries to come up with reasons why he is there. He eventually explains that he is there to woo her for Devadatta. Kapila says to himself that Padmini really needs a man of steel, and that Devadatta is too sensitive for someone as quick as Padmini.
The Bhagavata reveals that Devadatta and Padmini were quickly married, and that all three remained friends. The story then jumps forward six months, when Padmini is pregnant with a son, and the three friends are meant to go on a trip to Ujjain together. Devadatta expresses jealousy that Padmini seems to have some affection for Kapila, which Padmini denies. She says that she will cancel the trip so that the two of them can spend more time together, but when Kapila arrives, ready to leave, Padmini changes her mind and decides to go, much to Devadatta’s dismay.
As the three of them travel together, Padmini remarks how well Kapila drives the cart. She points out a tree with the Fortunate Lady’s flower, and Kapila rushes off to grab flowers for her. Padmini remarks to herself how muscular Kapila is, and Devadatta sees Padmini watching him with desire. When they pass the temple of Rudra and Kali, Devadatta is reminded of his old promise and sneaks away to cut off his head. Kapila goes to look for him, and upon discovering Devadatta’s headless body is struck with grief. He decides to cut off his head as well.
Padmini begins to get worried about the two men and goes after them. She sees their two headless bodies on the ground and attempts to commit suicide as well. The goddess Kali stops her and tells her she will revive the men if Padmini replaces their heads on their bodies. Padmini, in her excitement, accidentally switches the two heads when she replaces them. The two men are revived: one with Devadatta’s head and Kapila’s body, and the other with Kapila’s head and Devadatta’s body.
At first, the three of them are amused by the mix-up, but when they try to return home, they discover issues. Each man believes that Padmini is his wife. Devadatta’s head claims that the head rules the body, and so she is his wife. Kapila’s head argues that his hand accepted hers at the wedding ceremony, and that the child she is carrying came from his body. Padmini is aghast, but decides to go with Devadatta’s head. Kapila does not return with them.
As the second act opens, Padmini and Devadatta are happier than they’ve ever been. She loves his newfound strength, and the two of them prepare for their child. They buy two dolls for their son. The dolls speak to the audience and reveal that over time, Devadatta’s new, strong body begins to revert to its old form. He and Padmini fight over how to treat their son, as she believes that Devadatta coddles him. The dolls tell the audience that Padmini begins to dream of Kapila. When the dolls begin to show signs of wear, Padmini asks Devadatta to get new ones and goes to show her son the forest.
As Padmini travels through the woods, she discovers Kapila living there. He has regained his strength, just as Devadatta has lost his. He explains how he had to war against his body, and how he has come to accept that he is, in fact, Kapila. Padmini implies that she is attracted to him, and spends several nights with him.
Devadatta returns with the dolls and tries to find Padmini in the woods. He discovers her with Kapila, and the two decide to kill each other to put an end to the struggle between their heads and their bodies. After they have killed each other, Padmini decides to perform sati, throwing herself on their funeral pyre. The Bhagavata explains that Padmini was, in her own way, a devoted wife.
Just as the audience believes the play has ended, a second actor comes onstage saying that there was a horse walking down the street singing the national anthem. The first actor also enters, with a young boy in tow. The boy is very serious, and does not speak, laugh, or cry. It is revealed the child is Padmini’s son.
At that point, Hayavadana returns. He explains that he had asked Kali to make him complete, but instead of making him a complete human, she has made him a complete horse. Padmini’s son begins to laugh at Hayavadana, and the two sing together. Hayavadana still wishes to rid himself of his human voice, and the boy encourages him to laugh. As Hayavadana laughs more and more, his laughter turns into a horse’s neigh, and he thus becomes a complete horse.
The Bhagavata concludes the story by marveling at the mercy of Ganesha, who has fulfilled the desires of Hayavadana and the young boy. He says that it is time to pray, and Padmini, Devadatta, and Kapila join in thanking the Lord for ensuring the completion and success of the play.