[2] The bulk of the narrative describes a dream vision experienced by its central character, Rhonabwy, a retainer of Madog, in which he visits the time of King Arthur.

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.

Serving as his guide is one of Arthur's followers, Iddawg 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).

A colophon at the end declares that no one is able to recite the work in full without a book, the level of detail being too much for the memory to handle.