Jessica Jenkins has always been a perfectly ordinary girl - until one day part of her arm vanishes in the middle of geography class! Jessica's friends Izzy and Tom are determined to help her develop her newfound invisibility, though Jessica is more concerned with discovering where the ability came from. When it becomes apparent that there may be other kids developing strange powers of their own, Jessica marshals them into a slapdash band of "slightly superheroes." But when an unscrupulous adult discovers the origin of their powers and kidnaps one of the team, the rest must put their heads - and all of their skillstogether to avert disaster.