Leonora isn't supposed to be building a submarine in a tree. Or turning the local wildlife luminous. In fact, she is supposed to be keeping her head down and drawing no attention - because Leonora Bolt is an inventor in secret.

But she can't stop thinking of the clues she found to her missing parents' location. So, deep in hiding in Snorebury, desperately trying to avoid being discovered by her evil uncle, Leonora is hatching a plan.

So what if involves launching a homemade submarine into the middle of the ocean, accompanied only by a couple of friends and an otter with particularly sensitive whiskers? For when disaster strikes, Leonora's wackiest plan might just be her most brilliant yet...