Etain was the second wife of Midhir, a faerie king of Bri Leith. His first wife was jealous of the beautiful Etain and through magical help turned Etain into a small fly, who was blown into the mortal land and spent seven years in misery.

At the end of seven years Etain was blown into a hall during a feast, and fell from the roof into the cup of a lady, who swallowed her with the wine. Nine months later the lady bore Etain, who grew into the most beautiful woman in Ireland. She wed Eochaid, the High King, who took her back with him to Tara.

Throughout this time Midhir had known where Etain was, and approached her one day. He told her she had best come with him, for he was her first husband long ago, and that his first wife had placed a spell on her to send her out of Tir Nan Og. Etain said that she would not leave Eochaid to go with a stranger. Some time later Midhir appeared to her again and begged her to go with him. She agreed that she would only go if Eochaid gave her leave.

Soon after, Midhir came to Eochaid and challenged him to three games of chess. Custom allowed the winner to name the stakes, and Eochaid won the first two games. Midhir satisfied Eochaid's requests, and won the third round himself. He named Etain as his prize, but Eochaid refused, so Midhir instead asked for the right to put his arm around her and kiss her. Eochaid agreed to that, and at the end of the month Midhir returned to have his request granted.

When Midhir had entered the hall the doors were barred and all of Eochaid's forces were drawn around him so that Midhir could not carry Etain away. Midhir put his arm round Etain and kissed her, then they rose upward through the roof, and those outside saw two swans flying away, linked by a golden chain.