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.