Hywel, the King of Dyfed, falls in love with Elen, the beautiful young daughter of the deceased King of Dyfed. Their betrothal makes political sense, as it unites the two kingdoms, but their love for each other is genuine. Hywel becomes a just and wise king, introducing reforms to the Welsh legal system and forging alliances with neighboring kingdoms.

After going on a pilgrimage to Rome to get his law code approved by the Pope, Hywel gets caught up in political intrigue and seduced by a powerful Roman noblewoman. Back in Wales, he has to deal with a rebellion by the eldest son of the deceased King of Brycheiniog. Despite these challenges, Hywel strives to be a virtuous and enlightened king, and remains beloved by his people.

Based on the life of a true historical figure, John Broughton's 'Hywel The Good' is the story of one of the most important characters in Welsh history, remembered for his reforms to the Welsh legal system, and his efforts to unite the kingdoms of South Wales.