Like all children of his age, Arthur is fascinated by the bedtime stories his grandmother tells him. His dreams are full of African tribes and incredible inventions drawn from an old book of spells that belonged to his grandfather, who disappeared mysteriously four years ago.

What if all these tales are true? What if there really is treasure hidden at the bottom of their garden? And what if the Invisibles, the adorable tiny creatures sketched by his grandfather, really do exist? Now that could help save his family’s home, which is under threat from an unscrupulous property developer!

Arthur is about to find out as he uncovers a secret message that catapults him into an adventure wilder than he had ever imagined. In just three days, he must find a way to the land of the Invisibles, recover a stolen treasure, battle an invading force of mosquito-riding warriors, defeat an evil wizard, win the heart of a very independent princess and somehow get back home again.