Skeleton twins Rylie and Wylie are worried about their uncle Skulgar. They haven't seen him since he set off across the ocean in search of the master builder, Maestro. But Maestro has just shown up at their doorstep with terrible news: Skulgar has disappeared! The twins and Maestro join forces with Terry, Pim Pim, and Jane, who journey to Mystery Island to confront Skulgar's mysterious kidnapper. Continuing the epic graphic novel series set in the world of Clash of Clans and Clash Royale, Gene Luen Yang pens an offbeat and action-packed tale that turns the fantasy-adventure genre on its head!