The New York Times bestselling series returns! Zander and Natasha must reverse an evil spell threatening the Number Nine Plaza's very existence in this puzzle-bending mystery--for fans of The Swifts.

Summer is in full swing at The Number Nine Plaza, the world's largest and most fabulous department store, and best friends Zander and Natasha are looking forward to weeks of discovery after thwarting the vengeful Darkbloom's attempt to destroy The Nine. But has the danger truly passed? Store employees begin acting oddly, a long-lost clue to an ancient store mystery is uncovered, and Zander and Natasha themselves become targets for attack. When a devastating magic spell places The Nine under new peril, the two friends find themselves in a race against the clock to solve the store's ever-deepening riddles and preserve the world-famous Number Nine Plaza from destruction.

Featuring word puzzles, clues, and lavish illustrations, this enchanting, out-of-this-world mystery delivers an unforgettable read full of magic and adventure.