Thorgal and his family have left Arachnea's island to continue seeking a place to live in peace. As they sail along unknown shores, they're attacked by pirates, then rescued by Prince Zarkaj, who takes them to his palace and pampers them, especially Aaricia. But when Jolan and his mother turn out to have caught the terrible Blue Plague, the prince has them thrown into a guarded pit to die, and it's up to Thorgal to escape in search of a cure.