The story begins with the royal family—a woman of common birth caught the eye of the prince, and when the prince's father died, they were crowned king and queen. The queen gave birth to a second son during a summer of great drought. However, the child was wolf-like and inhuman, so the king had a giant maze built underground and placed his son inside.
A beautiful girl named Kima was born to a poor family, and with her birth came the end of the drought. Kima's parents had a second daughter, Ayama, who was so ugly that her parents treated her like a servant. Only Kima and Ma Zil showed Ayama kindness.
One dry day, the beast escaped from the labyrinth and soon after, townspeople noticed their livestock dead. The king offered a high reward for someone to forge a truce with the beast on behalf of the kingdom. Ayama's parents planned to move to the coast to escape, but Ma Zil suggested they send Ayama as the messenger. Ayama ventured across the wild lands to a forest of thorny trees and stopped at a pool of water.
The beast appears and speaks to Ayama about the cowardice of the king's men and the beast's own situation. He tells Ayama that if she can tell him a story that makes him feel an emotion other than anger, he will let her live. Ayama tells one of Ma Zil's stories:
A boy eats endlessly and is never sated, living in hunger and misery. A wise doctor examines the boy and concludes that he must eat a bit of the sun to counteract the night in his body. The doctor's daughter takes the boy across the western sea and scoops up a piece of the sun. The beast interrupts Ayama, disparaging that the story will end with the boy returned to mundane happiness. Ayama quickly changes the ending to the story—although the boy is no longer starving, he is still unhappy, and must simply endure the feeling of emptiness.
The beast gives Ayama a sprig of quince blossoms and lets her leave the thorn wood. When she returns to the town, the people do not believe she met the beast until she shows them the sprig of magical quince. The king is impassive, but his wife and human son are thrilled by Ayama's victory. Her family is given the promised reward and Ayama resumes her servant-like life at her home.
Soon, the people find their crops destroyed, and the king again calls for a messenger to meet with the beast. Ma Zil again encourages Ayama to return to the thorn wood. The beast again tells her of his mistreatment by the king, but Ayama suggests that he could learn to behave differently from his father. Ayama tells a second story at the beast's request:
The two children of Mama Tani are sickly and disobedient, causing Mama Tani much trouble. An evil spirit begins to harass the house and the children especially. The beast posits that the story will end with the children promising to be good and the spirit departing, as a warning to ungrateful children. However, Ayama has rewritten the ending—the spirit is revealed to be the children of Mama Tani's first children, who she killed with poison in order to garner sympathy from her village. The spirits' harassment kept the new children safe from Mama Tani's sickening poisons. The children tell their father, who sends a messenger to Mama Tani's first town (where she killed her first children), but by the time the messenger returns, Mama Tani has left the village again. The beast wants a bad ending for Mama Tani, however, so Ayama decides she was killed by coyotes.
Again, the beast gives Ayama a sprig of quince blossoms, though both she and the beast are reluctant for her to leave the thorn wood. The king rewards her family with a large estate, but before she leaves, the he tells her to return to the thorn wood a third time to kill the beast. He gives her a special knife made from thorns, since regular blades cannot pierce the monster's skin. Ayama agrees, but forces the king to promise that even if Ayama fails to return, he will give Kima the rewards and allow her to marry the human prince.
At the thorn wood, Ayama tells a third story: The youngest of three sisters cares for an ugly bird while her sisters spend their nights partying. After a week, the bird transforms into a handsome prince, who offers the girl his hand in marriage. The king and queen, however, dislike the peasant girl and set a series of challenges for her to accomplish. The two older sisters quickly ride to the palace and demand the prince return their sister to them. Thanks to their partying, the sisters are wary of handsome faces and fine titles, and tell the prince that he is unworthy of their sister, since he does not love her enough to defy his parents' challenges. The youngest agrees, and the three sisters return home and go to parties together.
Ayama reveals the king's knife. The beast tells her that he did not destroy the peoples' crops and livestock, and Ayama decides not to kill him. Instead, with his permission, she binds him and brings him to the palace. Ayama tells the king that she loves the beast and reveals that the king was responsible for destroying the peoples' herds and fields. The king's men attack Ayama, but she is unharmed; she reveals her new monstrous characteristics. The queen admits the king's treacherous ways, and Ayama has the king sentenced to the labyrinth he created.
Ayama and the beast marry, and Kima and the human prince marry, too. Ayama and the beast rule the kingdom, beloved by their people and feared by their enemies.
- Ayama - A young girl sent by the king to bargain with the beast.
- The beast - The disfigured child of the king and queen, whom the King trapped in a labyrinth.
- Kima - Ayama's beautiful sister.
- Ma Zil - Ayama's grandmother, who sends Ayama on her journey to meet the beast.
- In the author's note of The Language of Thorns, Bardugo mentions that the legends of Tarrare's polyphagia appear in Ayama's first tale in "far gentler form." Tarrare was a French man in the 1700s who suffered from an endless appetite, for which doctors could find no cure.
- Ayama and the Thorn Wood seems inspired by the fairytale Beauty and the Beast, with elements of Cinderella, A Thousand and One Nights, and the myth of the Minotaur.