Two owl detectives solve a Halloween mystery in this installment of a charming early reader series, perfect for fans of the Owl Diaries. In the fourth book in the Wallace and Grace series, the two owl detectives are confronted with a Halloween costume contest catastrophe when three contestants all claim credit for the same idea. These best friends are partners in the Night Owl Detective Agency and work together to solve mysteries! When Lukas the fox, Ava the opossum, and Mateo the squirrel all show up to the Owl-o-ween party with the same costume, no one knows whooo had the idea first—or whooo should win the delicious boo-berry pie. Can Wallace and Grace uncover clues to solve this costume mystery? Young readers will delight in this accessible Halloween story, the perfect pathway to chapter books.