Before the play begins . . .
Years ago, Creusa abandons the baby that Apollo had fathered on her in a cave outside Athens. Apollo sends Hermes to rescue the baby and bring it to Delphi, Apollo’s sanctuary. Creusa is later married to Xuthus, even though he is not Athenian, and they have been childless.
In the play . . .
Hermes tells us the ugly history of Creusa and Apollo, and he says that Xuthus and Creusa are on their way to Delphi to ask about whether they will have any children. The god also reveals that Creusa’s baby is now a youth who attends the temple, and he will soon be given the name Ion and be reunited with his mother.
Ion emerges to sweep the temple courtyard and other chores, and we meet the chorus of Athenians who attend Creusa. She soon arrives, ahead of Xuthus, and talks with Ion about why she’s in Delphi. Ion reveals he’s an orphan brought up at the sanctuary, and Creusa wonders about the baby that “a friend” abandoned years ago after Apollo had assaulted her. When Xuthus arrives, Creusa asks that Ion not mention their conversation.
Xuthus is confident of receiving good news, and he goes into the temple after making sure what’s allowed, and Creusa leaves for other altars. Ion worries over divine misbehavior that never gets punished, especially sleeping with mortal women.
The Chorus sing a song in honor of Artemis and Athena about the joys and sorrows of having children.
Xuthus comes out from his visit to the oracle and runs into Ion immediately, which Xuthus reveals is the sign that Ion is his son. Ion is skeptical, but Xuthus embraces him and starts to make plans to return to Athens, which Ion eventually accepts. The Chorus worry about Creusa’s reaction, and they sing with hostility for both king and new son, since they’re outsiders to Athens.
When she returns, Creusa learns about Ion, and she suspects her husband of infidelity, and she’s sure that Apollo has completely abandoned her and her baby. She reveals her sad history to an old retainer of her father’s, and the Old Man and the Chorus encourage Creusa’s worst worries about life in Athens with a foreign husband and an interloper stepson, and they come up with a plan to poison Ion.
The Chorus sing a song hoping the plot will succeed and praying for Ion never to come to Athens.
But a Servant comes on to tell how the plot failed and say that the Delphians are trying to find Creusa to punish her. She arrived, chased by a crowd and by Ion, and takes sanctuary at the temple. A Priestess appears with the tokens that Ion was abandoned with, and Creusa and Ion finally recognize each other as mother and son.
The play ends with the appearance of Athena, who confirms that Apollo is Ion’s father, instructs Creusa and Ion not to reveal that to Xuthus, and foretells that Ion will be the ancestor of the Ionians.