In the time before the flood, Noah is sent a message by a man called Bioth, to know whether he and his daughter Ceasair could have a place in the ark to save them from the flood. Noah responds that they should not get that. Ceasair’s husband, Fionntán, asks the same, and is similarly denied.
Bioth, Fionntán and Ceasair decide to consult and make plans. Ceasair advises them to forsake the god of Noah and to make an idol. The idol instructs them to make a ship and to go out to sea, but it is unable to tell them at what time the flood will come. They build the ship accordingly and set out, taking on board with them, 3 men: Bioth, Fionntán and Ladra (who is Ceasair’s brother); and 50 women, among them: Ceasair, Barrann and Balbha.
They are on the sea for seven years and a quarter until they put into port at Dún na mBarc.
It is suggested that they landed in Ireland, because being previously uninhabited, it was thought to be free from sin, and so, should escape the deluge.
They proceed to Bun Suaimhne or Cumar na dTrí n-Uisce, which is named for being the junction of the rivers An tSiúr, An Fheoir and An Bhearú. There, Ceasair divides the women into three groups and assigns each one a consort from the men.
They make no divisions of the land, as later groups did. Ladhra takes his share to what became known as Ard Ladhrann, and he got his death there. Balbha and Ladhra’s other women returned to Ceasair, who sent them to Bioth.
Bioth gets in touch with Fionntáin, so that they share Ladhra’s women evenly between them. Bioth goes to Sliabh Beatha in the north, and it is not long afterward that he gets his death. The bereaved women left after him come to Fionntáin at Cumar na dTrí n-Uisce. Fionntáin, intimidated at the weight of the task before him, and takes flight over the mountains, Sliabh gCua and Sliabh Caoin and then Tultuinne, where he puts on himself the form of a salmon so that he might escape them.
Ceasair goes with her people to Cúil Ceasrach until eventually the estrangement of her husband and the death of her brother and father cause her heart to break, whereupon she dies and is buried under Carn Ceasrach.
There was not six days from that until the flood, and all of her people drowned.