Return to the town of Little Spring Valley in this new series of illustrated chapter books for readers 7 to 10, based on the classic Mrs. Piggle-Wiggle books. "Betty MacDonald's beloved Mrs. Piggle-Wiggle always had one-of-a-kind ways to remedy children of their annoying or impolite habits. Now, nearly 70 years later, her singular magic can enchant a new generation, thanks to this delightful contemporary follow-up from [Ann] Martin, writing with MacDonald's great-granddaughter, [Annie] Parnell."—Publishers Weekly (starred review)

Once in a generation, "the Effluvia" strikes Little Spring Valley, and it affects everyone differently. In this third book in the series, Missy wakes one morning to find the Upside-Down House is … right-side up? It's not long before Missy has to quarantine the house, but meanwhile she's still fielding calls from worried parents, and it seems Louie can't keep his sticky fingers from taking other people's things. But Missy's magic cure might just do the trick, and even teach some valuable lessons along the way.