The New York Times–bestselling series continues with a haunted house whodunit that will take all of the Questioneers' sleuthing skills to solve.

Iggy Peck is an architect at his very core: When he's not making houses out of food, his head is up in the clouds, dreaming of design. So he's totally blown away when Ada Twist's Aunt Bernice inherits an old house from ice-cream mogul Herbert Sherbert that is filled with countless rooms from all his favorite architectural periods. But something's not quite right . . . Everyone says the house is haunted, and it seems that a number of priceless antiques—which were supposed to help Aunt Bernice pay for the house's upkeep—have gone missing. If they can't find those antiques, Aunt Bernice might lose the house forever. It will take all of Iggy's knowledge of architecture and the help of the other Questioneers—Rosie Revere, Ada Twist, and Sofia Valdez—to solve the mystery and find the treasure!