The eccentric scientist Petty Potts is refining a serum she has invented. But she has to keep it safe from a scheming rival, and from the twins Josh and Danny who seem to keep getting in the way and unfortunately falling victim to its powers. The boys turn into crane flies, beetles, spiders and various other insects in the series of books. They have all sorts of adventures where they have to resist the lure of bright lights, avoid getting eaten by dogs, and risk being swatted or becoming specimens in the jars of children fishing from ponds. The books are funny and witty, with plenty of toilet humour too. They are great for boys and girls, and each book has puzzles, games and quizzes at the back as well as links to websites and lists of fascinating facts about insects, so there's an educational element too!