He visited her at Forgall's house at Lusk, County Dublin, and wooed her by trading cryptic riddles with her.
He came to Ulster in disguise and suggested that Cú Chulainn should train in arms with the renowned warrior-woman Scáthach in Scotland, hoping the ordeal would be too much for him and he would be killed.
An ally of Forgall's, Scenn Menn, tried to stop the fleeing couple, but Cú Chulainn killed him in single combat at a ford.
When Aífe's son Connla came to Ireland in search of his father, Emer realised who he was and tried to persuade Cú Chulainn not to kill him, but to no avail.
Emer was said to possess the six gifts of womanhood: beauty, a gentle voice, sweet words, wisdom, skill at needlework and chastity.
This play is one of his five famous Cú Chulainn pieces, and is written with heavy stylistic influences from the Japanese Noh theatre.
Jealousy premiered in Amsterdam in 1922, under the direction of Albert van Dalsum with masks created by the sculptor Hildo Krop.