Dagda had an affair with Boann, wife of Nechtan. In order to hide their affair, Dagda made the sun stand still for nine months; therefore, Aengus was conceived, gestated and born in one day.
Aengus fell in love with a girl he dreamed of. His mother, Boann, searched Ireland for an entire year. Then his father, Dagda, did the same. Finally, King Bov the Red of Munster found her after a year.
Aegus went to the lake of the Dragons's Mouth and found 150 girls chained up in pairs. He found his girl, Caer. On November 1, Caer and the other girls would turn into a swan for one year. Aengus was told he could marry Caer if he could identify her as a swan. Aengus succeeded. He turned himself into a swan and they flew away, singing beautiful music that put all its listeners asleep for three days and nights.
Aengus and Caer had one son, Diarmuid Ua Duibhne.
Alternative: Aengus the Young, Angus, Anghus, Aonghus, Angus Og, Aengus mac Oc, Oengus mac Oc