Tom and Twigs want to learn red magic with a mysterious new guru called Muru, but to do it they need a red crystal which can only be found in the deepest, darkest caverns. Squirmtum guides them, but when Zigzoo's shiny new Mega Torch 4000 breaks, everyone is plunged into darkness! To make things worse, Squirmtum's friend Flicker vanishes, captured by the Mushas who want to use him to find their own red crystal. Will they ever get out of the caverns? Will Tom ever learn red magic? And where is Muru?