After their defeat by the Gaelic people, the Tuatha de Danann chose Bodhbh Dearg as their new king. Lir was offended by this choice, but Bodhbh offered him one of his foster-daughters in marriage, and so they were reconciled. Lir married Aobh, and they had two sets of twins; a boy and girl called Aodh and Fionnuala, and two boys called Fiachra and Conn, during whose birth Aobh died. Lir was heartbroken, but Bodhbh gave him as a second wife his foster-daughter Aiofe, the sister of Aobh.

At first Aoife loved her stepchildren, but she became jealous of Lir's affection for them and plotted their destruction. She took them out to a lake with the intention of killing them, but she could not bring herself to use the sword, so instead she turned them into swans. Fionnuala begged Aoife to tell them how long they would stay like that, and Aoife said it would last until a noblewoman from the south married a nobleman from the north.

When Bodhbh discovered what Aoife had done, he turned her into a demon, but there was nothing he could do for his children. For three hundred years, the swans remained on the lake, conversing with the Tuatha by day, and singing beautiful music by night. Following this, they spent three hundred years in cold and misery on the Sea of Moyle. After this, they spent a further three hundred years off the coast of Co. Mayo, where they endured even greater misery. At the end of that time, they flew back to their father's dwelling, but found the place lonely and deserted. Heartbroken, they returned to the west and met with the missionary St.Mochaomhog, who showed them great kindness.

Not long after that, the Connaught king Lairgnean married Deoch, the daughter of the king of Munster. Deoch wanted the four wonderful swans as a wedding present, and Lairgneach came to sieze them. However, their period of enchantment was over, and they turned into three withered old men and an old woman. The saint baptised them and they died happily and were buried together.