Cordelia Clay loves the work she and her father do together: saving and healing the remarkable creatures around Boston at the end of the nineteenth century. Their home on Cedar Street is full to the brim with dragons, squelches, and diggles, and Cordelia loves every one of them. But their work must be kept a secret, others aren't welcoming to outsiders and immigrants, so what would the people of Boston do to the creatures they call 'monsters'? One morning, Cordelia awakens to discover that her father has disappeared, along with nearly all the monsters. With only a handful of clues and a cryptic note to guide her, Cordelia must set off to find out what happened to her father, with the help of her new friend Gregory, Iggy the farting filch, a baby dragon, and a small zuppy (zombie puppy, that is).