Oh no! Mad scientist Petty Potts just turned up at Josh and Danny's summer camp, as the new camp counsellor. And she just happens to be hiding some bottles of extraordinary serum inside her raincoat . . . that can turn them into amphibians! Josh and Danny vow to stay away from Petty's SWITCH formula, but when their new friend Charlie gets into trouble, they know there's only one thing for it. Find Petty and get hopping! If everything goes to plan they should be back in plenty of time to perform in end of camp play . . . if the webbed feet EVER wear off!