Josh and Danny can't wait to try out Petty Potts's crazy new formula-a spray that will turn them into lizards!

Soon, they're making the most of their amazing speed and agility by whizzing up a tree. But in no time they're in deep doo-doo. Surrounded by bird poo and in serious danger of being swallowed whole by two moody owls . . .

Petty's back with a new kind of SWITCH spray-reptoSWITCH! The lizard formula is ready for testing, and Josh and Danny are eager to help. But as Josh and Danny are trying it out in the safety of Petty's secret underground lab, they're interrupted by an intruder's attempt to get in to Petty's house! The intruder vanishes, but there is a package waiting for Josh and Danny at home containing a marble and a cryptic clue.

Will Josh and Danny find the next mysterious marble? And will they be able to work out who sent the clue, and why?

Praise for SWITCH

This book has helped my son, 5, move on from picture books at bed time to one with more words. An excellent choice for reluctant readers who will be thrilled at the idea of turning into a bug, mad inventors and lots of adventures.

The book is great fun and involves the reader, who really feels as though they are part of the story. Along the way the reader learns a surprising amount about pond life.

Praise for Ali Sparkes's Frozen in Time, winner of the Blue Peter Book of the Year Award

'I know now what they mean by a plot that is toe-curlingly good . . . brilliantly inventive and rollicking fantastical adventure'

'Frozen in Time shows [Ali's] skill at fusing traditional children's storytelling with modern tales . . . Sparkes's sci-fi conspiracy thrills will keep 21st-century kids transfixed'

'It was outstanding. It blew me away'