Nancy, George, and Bess are attending a three-day overnight camp at the local zoo. They'll get to spend lots of time with all of the animals and learn about them too. The best part is, they will be helping the zookeeper make toys for the animals — just like real staffers! But when the toys the girls make by day are disappearing at night, it looks like everyone is a suspect! Can Nancy tame this wild case, or will the zoo animals be without anything fun to do?