Timmy is an only child and has just moved into an old house with his Mum and Dad a day before his ninth birthday. While his Mum prepares his birthday dinner, he manages to force the strange door under the stairs to open. He soon finds out the door leads to a dirty old cellar full of junk. While exploring in the cellar he spots an old trunk shut tight with age.
Suddenly the trunk slowly vibrates then bursts open! He rushes over and looks inside, soon to discover The Secret in the Cellar. Timmy has been chosen to deliver The Book of Rule to The Golden King of Inner Earth with the help of Nanos, the Keeper of the Book. But it is not a simple as all of that, as the evil Wizard Bathos also wants the book and will stop at nothing to get it. Timmy is taken on an adventure full of dragons, flying carpets, monsters, and wizards.