Mice chewing up the documents at McGurk's basement detective office make trouble enough, especially with the Organization's first Open House just a few days off; but when an anonymous note makes clear that the mice were planted, McGurk gets good and mad. And though Brains Billingham's Ultrasonic Transmitter gets rid of the mice, the culprit pulls a more daring switch right at the Open House: with Patrolman Cassidy himself on hand to unveil the handcuffs he gave the McGurk Organization for helping solve The Case of the Nervous Newsboy, the assembled guests watch in horror as the curtain parts to reveal not handcuffs but a pair of realistic fake mice. Well, McGurk's anger soon becomes constructively directed, and the five young detectives puzzle out some far-fetched clues in the note to track down both the handcuffs and the young perpetrator. As always, the brisk detection will keep readers on their toes without leaving them behind.