On the fifth year of their marriage, Procne asked her husband to go to Athens and bring Philomela back, as the two sisters hadn't seen each other for a long time. Tereus agreed and went to Athens, where Pandion I told Tereus to take care of her, as if he were her father. However, on the way back to Thrace, Tereus gave in his lust for Philomela and raped her. He then threatened her not to say anything to her sister, but Philomela was defiant, angering him. So, he cut off her tongue and abandoned her. When he returned to Thrace, he told Procne that Philomela had died.
Philomela, however, although unable to speak, managed to weave the crime onto a tapestry and brought it to her sister. When Procne found out what had happened, she killed her son Itys, boiled him, and served him to Tereus. Unaware, Tereus ate the meal, and he only found out when Procne and Philomela presented the severed head of Itys to him. Tereus grabbed an axe and started chasing the two sisters, who fled and started praying to the gods. The gods answered their prayers and turned all three of them into birds; Procne into a swallow, Philomela into a nightingale, and Tereus into a hoopoe.