Wallace and Grace and the owl-o-ween mystery

"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 ide...