In his last year of primary school, Albert becomes lost while escaping from bullies. He finds himself in an underworld of storm-water drains and sewers, where he befriends an ageing rat, a small bird and a crazy echidna.

His new friends believe his visit is the fulfilment of a prophecy that he will save the animals from the control of the evil King Rat and his mistress, the Witch. All Albert wants is to get home, but secretly the animals defy his wishes and set him on course with the prophecy.