During their last attack, the Burnham Raiders almost succeeded in destroying the castle gate of Novelmore. Only a brilliant idea from Dario saved the inhabitants of Novelmore from a storming of their castle. But now the castle gate urgently needs to be reinforced... but how? Dario has heard of a rare metal that is considered indestructible. However, this metal is not found in Novelmore, but only in a mine in the Crimson Caldera! Of course, King John is strictly against an expedition there, but Arwynn, Gwynn, and Dario have never let his concerns stop them. So the three friends embark on a new adventure into enemy territory - and make a very dangerous discovery there.