Lucius, the narrator, is journeying to Thessaly. On his way he meets a man named Aristomenes, who tells him a story of Socrates, a friend of his whom he encountered along the road. Socrates had fallen in with a witch, who later killed him and frightened Aristomenes. Lucius believes the man’s story and is intrigued.
In Thessaly he stays with Milo and his wife, Pamphile, a notorious witch. Lucius encounters his aunt, Byrrhena, who warns him of Pamphile. While in town Lucius is also the centerpiece of the festival of Laughter when, drunkenly, he stabs three wineskins thinking they are robbers and is taken to a fake trial.
Lucius begins to sleep with the maid, Photis. He begs her to let him watch Pamphile do magic, and Photis grudgingly agrees. They watch Pamphile turn into a bird, and after she leaves, Lucius clamors for the ointment she used. Photis accidentally gives him the wrong material, and he turns into an ass. He is terrified and angry, and Photis tells him the only way he can turn human again is by eating roses.
Milo’s house is robbed by a group of bandits, who take Lucius with him. He is beaten up and dragged to exhaustion. In the bandits’ cave they bring in a young woman whom they’d kidnapped from a neighboring town for ransom. The old woman who tends them tells the girl the story of Cupid and Psyche.
In this tale, Psyche is a beautiful mortal woman. She is isolated from her family when a prophecy says she will marry a winged monster. The wind Zephyr takes her from the top of a mountain into a valley and a splendid home, where her new husbands comes to her. It is Cupid, although he is invisible and does not reveal his true identity to her. He falls in love with her even though his mother Venus is deathly jealous of the girl’s beauty, and Psyche falls in love with him too. He warns her of her cruel and evil sisters, but she is too curious and easily swayed that she disobeys his commands and eventually severs the ties between them. He leaves her and she despairs, and seeks revenge on her sisters. She then tries to find Cupid and eventually decides to go to Venus to grovel before her. Venus loathes the girl and gives her impossible tasks to perform. Psyche receives help for all the tasks, including Cupid on the last one, as he decides he still loves her. Finally Jupiter intervenes and says Venus must be okay with her son’s wife. He makes Psyche a god, and she and Cupid have a daughter.
The old woman ends the story. Not long after, the kidnapped girl, Charite, is rescued by her new husband, Tlepolemus, and the townspeople kill most of the bandits. Lucius is honored and treated well, but he is given to a young boy as a caretaker; the boy is terribly cruel and vile, and is eventually killed by a huge bear.
News comes to the slaves of the household that Charite and Tlepolemus are dead due to the evil doings of a man named Thrasyllus, who was in love with Charite and schemed to get Tlepolemus killed. The slaves run away and take Lucius with them. Lucius is sold to a priest who, with other priests, is a catamite. The priests are at the center of a scandal and go to a new city. Lucius is almost cooked and served to dinner guests, but at that time rabid dogs attack the group and everyone is afraid Lucius is also sick.
Lucius is then sold to a baker, and is worked very hard. While working for him he hears and observes tales of adultery and betrayal. He is then auctioned to a farmer, who loses him to a soldier.
He stays with the soldier for a short time and is then sold to two brother slaves, one a baker and one a cook. Lucius eats their food when they are out of the kitchen, as he still likes human food. When the brothers catch him they are not mad, and the whole thing tickles their master. Lucius becomes a celebrity and the master lets people pay to see the ass eat human food. Lucius also garners the eye of a wealthy woman, who pays to have sex with him. The master then decides he will have a public display of Lucius having sex with a woman at his three-day carnival.
Lucius bemoans the fact that the woman selected for him is a criminal who killed her husband, his sister, her daughter, and the local physician and his wife all to satisfy her murderous jealousy and rage. Right before Lucius is supposed to come out for the show, he runs away; he cannot stomach the shame that would come from being with that woman.
Lucius falls asleep and when he wakes, offers a prayer to Isis, the great goddess. She comes to him and tells him how he can return to human form. A procession celebrating Isis comes by, and Lucius follows the instructions given him; he finds a priest with roses, eats them, and becomes a man again. The crowd is stunned and praises Isis. Lucius devotes his life to serving Isis, becoming one of her priests, joining her cult, and eventually entering the cult of Osiris as well.