Josh and Danny have lost their dog, Piddle, and sneak next door to try and find him. They get more than they bargain for when they run into their next-door neighbour, Petty Potts - a mad scientist with a gleefully beastly serum. One accidental squirt of the S.W.I.T.C.H spray later and the twins find themselves with eight legs and the ability to shoot webbing out of their bums! Josh and Danny are in big bug trouble as they face a dangerous journey across their back garden in the hope that Petty can SWITCH them back. But it's a big bad world out there and the brothers are no longer top of the food chain. Petty Potts's diary entry: I think it's high time I had some assistance on the SWITCH PROJECT . . . If only I could remember what happened to the rest of my research! I know I put the code for SWITCHing creatures to reptiles in the crystal cubes, as I did for the bugs and insects formula . . . and I know I hid the cubes somewhere safe from even me! I just can't remember. Victor Crouch has a lot to answer for. I will get my revenge on him. For burning out chunks of my memory and trying to steal my life's work.