It isn't normal to hear a voice coming from underneath a flowerbed but that's what Tim hears one day in his school playground.
No harm in investigating he and his friend Molly think - until a sly and power-seeking worm takes the opportunity to push Molly through a portal into a parallel world!
Falling through to the Underland, she hits a forgetting stone, completely wiping all her memories of home and Tim.
Now the only way to restore them is a dangerous soul quest... On her journey she meets many mystical beings including Hogmills, a talking raven, spirit guardians and - worst of all - The Great Illusionist, a being so hungry for power, she has torn the Underland's careful balance in two.
With Tim stuck in the human world, and Moly stuck in the Underland, the situation looks bleak.
Only together can they defeat The Great Illusionist and restore the balance of the Underland.
But will their friendship prove strong enough to conquer such utter darkness?