One day, a hot air balloon attached to a huge straw house, lands in the garden of the Dollybutt family.

He tells Mrs Dollybutt and her three children that he is going to find his brother, Perceval, who is lost in the jungles of Africa, looking for gorillas.

Lancelot takes the three children, Emma, Ivan and Conrad with him in the hot air balloon, which he has called Belladonna, to track Uncle Perceval.

On their way, they meet several animals which they can talk to (because of the dust), including a swallow, a camel and a fennec fox, who tell them many interesting facts about their lives.

In addition to the original plot, a villain called Lucretia Moore follows Lancelot and the children in their air balloon, and tries to sabotage their attempts to find Perceval, so she can steal the magic dust.