Arthur and his men learn that Mabon was stolen from his mother's arms when he was three nights old, and question the world's oldest and wisest animals about his whereabouts, until they are led to the salmon of Llyn Llyw, the oldest animal of them all. The enormous salmon carries Arthur's men Cei and Bedwyr downstream to Mabon's prison in Gloucester; they hear him through the walls, singing a lamentation for his fate. The rest of Arthur's men launch an assault on the front of the prison, while Cei and Bedwyr sneak in the back and rescue Mabon. He subsequently plays a key role in the hunt for the Twrch Trwyth.