It's the worst day of Mouse Formidable's life when he gets home to find his beloved flying machine gone and the Louds dismantling his barn. They're packing everything, and he fears that when they go they won't come back. 

With his whole world collapsing he stows away in their car and travels with the Louds into their world. Little does he know that someone is travelling with him. At the Loud's house fantastic discoveries are made, but then Formidable is caught in a trap. Will he be found before it's too late, and will he ever go flying again?

In the meantime, many miles away, back in the wood where he was born a fire starts. Mouse Formidable's family are in terrible danger. With nowhere to run who will save them? The Stowaways is a story of discovery, daring, and friendship.