The story is about a primary school teacher, Frans van der Steg, who has to rescue a child, Geert-Jan, from the hands of his uncle, Graaf Grisenstijn. Geert-Jan lives with his uncle in the Trappenhuis - a colossal house full of stairs - and never comes into contact with other children. His uncle has "locked him up" because in ancient writings of Count Gregory it is mentioned that there is a treasure (which was taken by the first Earl Grimbold during a crusade in the Middle Ages) in the Staircase, and that only a child can find it. find. The count wants Geert-Jan to find the treasure for him.