Derfel and his men undertake a night march to reach and capture Lugg Vale at dawn, ready to hold the position for when Gorfyddyd's main army arrives. The main army is led by Nimue, who has an uncanny ability to find her way in the dark. They succeed in taking the Vale and await Arthur there. Arthur arrives in time to destroy the vanguard of Gorfyddyd's army and sends Galahad south in the hope that the men of Gwent will come and fight now that they know battle has begun. Arthur then offers Derfel his unique armour, which will give Arthur the opportunity to spring a trap on the rear of Gorfyddyd's army and hopefully drive them into panic. Derfel is confronted by Valerin, who was betrothed to Guinevere before she ran off with Arthur. Believing him to be Arthur, Valerin tells Derfel that Guinevere was a whore; Derfel cannot control his temper and fights Valerin. After killing him, Derfel finds a lovers' ring on his corpse with Guinevere's symbol on it, which he throws away. The battle then resumes with Derfel's troops being forced into retreat until Morfans, another of Arthur's commanders, gives the signal for Arthur to attack. Arthur's charge destroys almost a third of Gorfyddyd's army, but the king sees the danger in time to defend against it. Arthur's trap has failed.