A Book of Myths, by Jean Lang - Umnet

"Well did I know thou didst bear me no love," said Conor, and black
was his brow.
He called for Fergus then, and Fergus, sore troubled, made answer that
were there to be such a betrayal, the king alone would be held sacred
from his vengeance.
Then Conor gladly gave Fergus command to go to Alba as his emissary,
and to fetch back with him the three brothers and Deirdrê the Beautiful.
"Thy name of old was Honeymouth," he said, "so I know well that with
guile thou canst bring them to Erin. And when thou shalt have returned
with them, send them forward, but stay thyself at the house of Borrach.
Borrach shall have warning of thy coming."
This he said, because to Fergus and to all the other of the Red Branch, a
geasa, or pledge, was sacrosanct. And well he knew that Fergus had as
one of his geasa that he would never refuse an invitation to a feast.
Next day Fergus and his two sons, Illann the Fair and Buinne the Red,
set out in their galley for the dun of the Sons of Usna on Loch Etive.
The day before their hurried flight from Erin, Ainle and Ardan had
been playing chess in their dun with Conor, the king. The board was of
fair ivory, and the chessmen were of red-gold, wrought in strange
devices. It had come from the mysterious East in years far beyond the
memory of any living man, and was one of the dearest of Conor's
possessions. Thus, when Ainle and Ardan carried off the chess-board
with them in their flight, after the loss of Deirdrê, that was the loss that
gave the king the greatest bitterness. Now it came to pass that as Naoise
and Deirdrê were sitting in front of their dun, the little waves of Loch
Etive lapping up on the seaweed, yellow as the hair of Deirdrê, far
below, and playing chess at this board, they heard a shout from the
woods down by the shore where the hazels and birches grew thick.
"That is the voice of a man of Erin!" said Naoise, and stopped in his
game to listen.