The novel is a retelling of the story of the First Branch of the Mabinogion, Pwyll Pendefig Dyfed (Pwyll, Prince of Dyfed), and hence is chronologically the first of Walton's Mabinogion novels, though published last.
The novel is a retelling of the story of the Third Branch of the Mabinogion, Manawydan Fab Llŷr (Manawyddan, son of Llŷr).
It follows three main characters who find themselves moving from their world in West Wales to the setting of the tales of Welsh mythology known as the Four Branches of the Mabinogi (Welsh: Pedair Cainc y Mabinogi, often referred to as simply Y Mabinogi), from which the film's title is derived.
Four Branches of the Mabinogi | Y Mabinogi | Restoration Branches | Organizational Structure of Jehovah's Witnesses#Branches and zones | List of Queens Library Branches | Glandular branches of the superior thyroid artery | Glandular branches of the inferior thyroid artery |
Gwawl, son of Clud, is initially mentioned in the first of the Four Branches of the Mabinogi, when Rhiannon tells Pwyll, Prince of Dyfed, who wishes to marry her, that she is intended for Gwawl.