Lucius, a man originally from the Greek part of the Roman Empire, is on a journey to Thessaly. He says he wants to tell a witty and wonderful story, but apologizes for his own poor Latin (since he grew up speaking Greek). Lucius is very interested in stories and often pauses his own story, either to recount a story he heard somewhere else or to listen to someone else telling a story. For this reason, Lucius’s journey tends to be episodic and full of stories within stories.
In an early encounter with a wayfarer named Aristomenes, Lucius hears a tale of witchcraft. Later, in the town of Hypata, he stays with a friend named Milo, who has a reputation for being a stingy host and whose wife, Pamphile, is rumored to be a witch. While staying at Milo’s, Lucius begins to secretly have sex with a maid named Photis.
One time when Lucius is with Photis, they witness Pamphile’s witchcraft firsthand. The two of them secretly watch Pamphile using an ointment to turn herself into a bird. Lucius is interested in getting his hands on the ointment, so he persuades Photis to help him. When Lucius tries out the ointment for himself, however, he is surprised to find that instead of turning into a bird, he turns into a donkey. Photis advises him that he can turn back into a human if he simply eats some roses, and that she’ll bring him some roses in the morning. Before she can come back with roses, however, Milo’s house is sacked by thieves, and Lucius (in the form of a donkey) is taken back to the thieves’ cave.
And so, thus begins Lucius’s journey to try to find roses and become human again. Because he is a donkey, people talk freely around him, and Lucius often witnesses or overhears some interesting stories. Perhaps the most elaborate story he hears is the story of Cupid and Psyche. An old hag who works with the thieves who sacked Milo tells the story to a hostage named Charite, perhaps as a way of comforting her. In the story, Psyche undergoes many hardships, partly because her beauty and her curiosity offend the goddess Venus. Ultimately, however, Psyche perseveres, and she is allowed to become immortal and live forever with her husband Cupid. Charite is later rescued by her fiancé, Tlepolemus, who kills all the thieves and sets Lucius off on the next leg of his journey.
Many of the stories Lucius tells or hears have less happy endings and involve unfaithful spouses getting caught in the act. All the while, Lucius is passed from owner to owner, suffering cruel treatment from just about everyone in charge of him, including the priest Philebus, the ass-boy, the baker, and the soldier. Lucius is whipped, overburdened, threatened with death, and at one point almost eaten.
The climax of Lucius’s mistreatment comes when he encounters the jealous wife. She has been accused of terrible crimes and so has been condemned to be executed by being torn apart by wild animals. Before the woman is torn apart, she will be forced to publicly have sex with Lucius (who is still a donkey). Lucius, fearing for his own life if the wild animals are unleashed, decides that the only thing to do is flee.
Shortly after Lucius escapes, he has a vision of “the mother of the universe,” a deity who ultimately reveals herself as the Egyptian goddess Isis. Isis instructs Lucius in how he can obtain a rose to turn back into a human, and Lucius enthusiastically accepts her help. By following Isis’s instructions exactly, Lucius is able to find a rose, eat it, and ultimately be restored to human form.
After saving Lucius, Isis asks for his devotion in return, arguing that it is only fair. Lucius is happy to offer veneration and gets involved with serving the cult of Isis. Later, he is visited by Osiris, the husband of Isis, and Osiris also asks him for his loyalty and service. Lucius enthusiastically agrees. In order to prove his devotion, Lucius shaves his head, moves to Rome, and takes up a legal profession. A loyal member of the cults of Isis and Osiris, Lucius proudly displays his bald head so that everyone will be aware of his devotion.