Twelve-year-old Teddy investigates when a popular Texas zoo's star attraction--Henry the hippopotamus--is murdered.

"For once, operations at the enormous zoo/theme park appear to be running smoothly (except for the occasional herring-related mishap in the penguin exhibit) and Teddy Fitzroy is finally able to give detective work a rest. But then a local lion is accused of killing a famous dog--and the dog's owner, an inflammatory radio host, goes on a crusade to have the cat declared a nuisance so it can be hunted. However, there's evidence that the lion might have...

While visiting a ranch near Yellowstone National Park with his parents, Summer, and her parents, Teddy Fitzroy investigates the disappearances of bison and an irreplaceable necklace.