Rory Rooney likes to be prepared for all eventualities. His favourite book is Don’t Be Scared, Be Prepared, and he has memorized every page of it. He could even survive a hippo attack. He knows that just because something is unlikely doesn’t mean it won’t ever happen . . .

But Rory isn’t prepared when he suddenly and inexplicably turns green. Stuck in an isolation ward in a hospital far from home with two other remarkably green children, Rory’s as confused by his new condition as the medics seem to be.