From the introduction:
Centuries ago, Avalon was not ruled by a Queen, but by a King. And he did not wield the Graal, but instead, a sword. A sword called “Caledfwlch.” With it, he conquered all of Avalon, uniting the Glamour Isles with war and bloodshed. In his later years, he lost the sword, and thus, he lost the kingdom. The Glamour Isles were divided again and would remain so for centuries. And, as the ancient prophets said, “He who holds the sword is the True King of all Avalon.”
Since then, scholars and historians have debated whether the story was history or legend, and now it seems the time to answer that question is at hand. The Explorer’s Society discovered clues leading to a cave where “the ancient blade rests, waiting to be awoken.” Unfortunately, a spy within the Society escaped with the clues, taking them to the Highland Marches where a Villain waits to discover the sword, throw Elaine off her throne and put all of Avalon under his heel. The Heroes must act quickly, for if they do not find Caledfwlch in time, all of Avalon may fall under a terrible, cursed reign…