When Ben Silverstein is sent to the rundown town of Buttonville to spend the summer with his grandfather, he's certain it will be the most boring holiday ever. That is, until his grandfather's cat brings home what looks like . . . a baby dragon? Enter Pearl Petal, a local girl with an eye for adventure, who helps Ben take the wounded dragon to the only veterinarian in town - the mysterious Dr Woo. No one knows where Dr Woo came from or why she's moved into the old button factory and renamed it Dr Woo's Worm Hospital. But as Ben and Pearl discover once they are inside, Dr Woo's isn't a worm hospital at all - it's actually a secret hospital for Imaginary Creatures. After Ben accidentally leaves the hospital's front door unlocked, a rather large, rather stinky, and very hairy beast escapes into Buttonville. Ben and Pearl are tasked with retrieving the runaway creature, and what started out as the most boring holiday ever becomes the story of a lifetime.