Petty's back with a new kind of SWITCH spray - repto SWITCH! 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?