Matty's quest is to find his father, who is a British soldier serving in Africa during the Second World War. The boy forms a friendship with Boxer, a homeless boy he discovers living rough in a disused brick kiln with a mouse called Smokey. Together with a stray dog they call Tonka the friends make preparations to sail to Africa in a stolen barrage balloon. Matty is sure the balloon will take him there and bring his father home again. But there are many strange happenings in the area around their home, and an evil presence known as the Devil Jack is determined to wreck their plans.