"Stocke awakens in the castle infirmary. Soon after, he and Sonja are attacked.
Rosch rescues Stocke and Sonja from the attack, but the invader turns to sand before he can be questioned.
Nobody is sure whether the Sand Plague, which causes people to turn to sand, is connected to the terrible desertification afflicting Vainqueur.
Even so, Stocke is ordered to keep the details of the attack under wraps."
White Chronicle