Three members of the family, young Dan Lind and his two relatives, Ingrid Lind and Ulvhedin Paladin, set out on the long journey north to the forgotten Valley of the Ice People.

Dan's objective for the trip was purely scientific, while the other two wanted to get hold of the powerful, magical root that they were convinced they would find there: the mandrake, also known as the gallows flower because it was said to grow at places of execution.