Nicholas confirms his aunt's suspicions by making it look as though he is trying to get to the gooseberry garden, but he slips back into the house. He puts his plan into action—a plan he has been developing in his mind for a long time. The plan involves Nicholas standing on a chair in the library to reach a shelf where lies a fat, important-looking key. The key can unlock the mysteries of the lumber room, where only aunts and authorized adults are allowed entry.
Nicholas has been practicing fitting keys into keyholes with the schoolroom door. Having practiced, he manages to get the lumber room door open. He enters an unknown land.