The
frame story tells that Madog sends Rhonabwy and two companions to find the prince's rebellious brother Iorwerth. One night during the pursuit they seek shelter with Heilyn the Red, but find his
longhouse filthy and his beds full of fleas. Lying down on a yellow ox-skin, Rhonabwy experiences a dream of Arthur and his time. Serving as his guide is one of Arthur's followers, Iddawg fab Mynio who is better known as Iddawg Cordd Prydain (the Churn of Britain), so called because he sparked the
Battle of Camlann when he distorted the king's messages of peace he was supposed to deliver to the enemy
Medrawd (Mordred). Iddawg introduces Rhonabwy and his friends to Arthur, who regrets that Wales has been inherited by such tiny men. Iddawg reveals that Arthur's men are assembled to meet the
Saxons at the
Battle of Mount Badon. However, Arthur is more concerned with a game of
gwyddbwyll, a Celtic board game similar to Roman
ludus latrunculorum, that he is playing against his follower
Owain mab Urien (
Ywain). While they play, messengers arrive declaring that Arthur's squires are attacking Owain's ravens; when Owain asks that this be stopped Arthur only responds, "your move". Finally Owain orders his ravens to attack Arthur's servants; when Arthur asks him to call them off, Owain says "your move, lord". Eventually Arthur crushes the chess pieces into dust, and the two declare peace between their forces. After this the Saxons send a contingent asking for a truce, which Arthur grants after consulting his advisors.
Cai (Kay) declares that any who wish to follow Arthur should come to
Cornwall. The noise of the troops moving wakes Rhonabwy, who realizes he has slept for three days. ==Interpretation==