The Reluctant Spy — Lois June Wickstrom

When Timmy spies a rat under his bed, he knows he has to get rid of it before Grandma finds out. But when Grandma enters his room, she introduces her little pet by its name, "Hildegarde." The rat is being trained to spy on a mad scientist neighbor whom Grandma suspects of causing a local earthquake. But when Hildegarde is trapped, it's Timmy who goes to the rescue. He has to become a Reluctant Spy himself! This juvenile novel employs real spy techniques, real animal training techniques, and real science to create an intriguing mystery with family values.