Encyclopedia Brown and the Case of the Two Spies by Donald J. Sobol

Encyclopedia Brown is a America's youngest detective. Thanks to his brilliant mind, no one, no matter how old, gets away with breaking the law. Since his father is the chief of police, he can use his skills to help his father when he's stumped. In the summers, he opens his own detective agency, and help the kids in his neighborhood. In this book, he help his father catch two mysterious spies, who some how manage to communicate in the bathroom. Can Encyclopedia catch the spies before it's too late? -AbdurRahman