Damian Drooth has already solved three cases to great acclaim (and uproarious chaos!), and now he is passing on his skills to eager pupils.

He has decided to help a friendly old man who thinks that his precious and hard-won inventions are being ripped off by an unscrupulous neighbour.

Naturally, the meeting of the Young Inventors is a good place to start - and using all his old skills, he does uncover the bad guy...