Derfel then spends three years in Benoic and learns quickly that Lancelot's fearsome reputation has nothing to do with his prowess in battle and everything to do with paying poets to sing his praises. Derfel and Galahad begin a campaign to slow the advance of the Frankish barbarian hordes. In this they succeed and become feared by the Franks. However, they are eventually pushed back to Ynys Trebes, where Lancelot has taken charge of defending the city. At a council of war, Lancelot insists that the kingdom can survive within the city's wall, as the city is self-sufficient. After several months under siege, the city falls. Lancelot, with his mother and followers and the kingdom's treasure, flees as soon as the city is breached. As a great massacre ensues, Derfel feels compelled to return to the palace, where he finds King Ban resigned to his fate and Father Celwin in the library frantically searching for a particular Roman scroll, both refusing to leave. As the Franks storm the palace, Father Celwin reveals himself to be Merlin in disguise. Merlin finds what he was looking for, saying that it contains the Knowledge of Britain. He then leads Derfel and Galahad out of the city and into a boat which he had already arranged for his escape.