Stuart Gibbs’s Belly Up (2010) is a middle grade mystery novel and the first book in the FunJungle series. The story’s protagonist and narrator is 12-year-old Teddy Fitzroy, who lives in a massive zoo and amusement park called FunJungle. When the park’s mascot, Henry the Hippopotamus, mysteriously dies, Teddy embarks on a daring and adventurous investigation to find the truth behind his death. Along the way, he makes allies and enemies, uncovers secrets, and faces grave dangers. The novel won the Great Lakes Book Award and the Pennsylvania Young Reader's Choice Award and explores themes of resourcefulness, bravery, and environmental ethics. Other books in the FunJungle series include Poached (2014), Lion Down (2019), and Whale Done (2023), among others.

This study guide uses the e-book edition released by Simon & Schuster Books in 2010.

Content Warning: The source material contains depictions of animal abuse, weight stigma, and problematic language about mental health concerns.

Plot Summary

Twelve-year-old Teddy Fitzroy lives at a large zoo named FunJungle where his parents work. One day, the zoo’s mascot, Henry the Hippo, dies unexpectedly. The park’s director of operations, Martin del Gato, tries to mitigate the guests’ distress and avoid bad press. Teddy hides and watches as Doc, the park’s head veterinarian, performs Henry’s autopsy. Doc discovers many tiny holes in the hippo’s small intestine and suggests he was murdered by being fed small, pointed objects. To Teddy’s shock, Martin orders Doc to state Henry died of natural causes in his report. Later that night, Teddy’s mother listens patiently to her son’s concerns, but she thinks the hippo’s death is an instance of humans’ senseless cruelty toward animals rather than an intentional killing. Teddy resolves to investigate Henry’s murder himself before the killer can strike again.

The next morning, Teddy finds a footprint outside his home and suspects someone is spying on him. At the zoo, he meets Summer McCracken, the 13-year-old daughter of the billionaire who owns FunJungle. To his surprise, Summer believes him when he tells her Henry was murdered, and she slips away from her bodyguards to join his investigation. Teddy and Summer sneak into the hippo enclosure, and she finds a sharpened jack in one of the pools. After Summer’s bodyguards escort her from the park, Teddy goes to the animal hospital and shows the jack to Doc. The veterinarian worriedly tells Teddy he shouldn’t know anything about Henry’s killing, takes the murder weapon, and sends the boy away. When Doc hurries into an operating room, Teddy catches a glimpse of a dead jaguar, which confuses him because the park doesn’t have jaguars on display.

Henry’s killer sends Teddy a text message claiming to be Summer. The message directs him to a reptile exhibit where a black mamba was set loose, but Teddy manages to escape without being attacked by the deadly snake. The young detective realizes he was set up by Henry’s killer, who is clearly willing to do anything to stop his investigation. Teddy tells his mother about the incident in the reptile house, and she informs Martin. The black mamba proves difficult to find, so the building is closed indefinitely. The security cameras were turned off, so there is no footage of the perpetrator who set the snake loose.

The next day, Teddy’s mother wants him to stay by her side, but he sneaks away and meets with Summer, who has a new lead on the case. Before Henry came to FunJungle, he was in a circus and bit the clowns. One of the clowns, a man named Charlie Conner, now works at the zoo. He tells Summer and Teddy he overheard the park’s head of public relations, Pete Thwacker, offering to pay a security guard named Marge to kill Henry. Teddy tells his mother what Charlie said, but she argues Pete and Marge lack the intelligence to devise the murder weapon used to kill the hippo. Teddy’s mother asks Buck Grassley, FunJungle’s head of security, to talk to her son. Concerned for his own safety, Teddy agrees to entrust the investigation to Buck.

During the grand opening of Carnivore Canyon, Summer introduces Teddy to her father. J. J. McCracken believes Henry was murdered by an animal rights organization or a rival corporation. At his request, Teddy agrees to leave the investigation in the adults’ hands. Suddenly, a hungry tiger escapes from its enclosure and lunges at Teddy and his mother. Teddy’s father, who just returned from an assignment in China, drives the tiger back. The animal charges into the grand opening party, which sends the guests into a panic. However, the zookeepers are able to return the animal to its enclosure without anyone being injured. Teddy tells his father about the sinister recent events at the zoo, and Mr. Fitzroy decides to join the investigation.

The next day, FunJungle publicly accuses an anti-zoo animal rights organization of releasing the tiger and killing Henry. Teddy and his father talk to the animal hospital’s secretary and learn an alarming number of animals already died at the zoo and most of them were from the Amazon. During Henry’s funeral that afternoon, Teddy and his parents sneak into the administration building with some help from Summer. The Fitzroys uncover a horrifying plan to add thrill rides to FunJungle’s enclosures, a move that would pursue profit at a severe cost to the animals’ well-being.

Buck Grassley arrests Mr. and Mrs. Fitzroy for breaking and entering and claims they are covert members of the animal rights organization that killed Henry. Teddy flees to Henry’s funeral with Buck and his security guards in close pursuit. During the chase, the crane transporting Henry’s coffin drops it, causing the corpse to burst. Teddy uses the chaos to run from the zoo’s premises. He thinks Summer set his family up and that Doc may be the only person he can trust to help him solve Henry’s murder and clear his parents’ names.

Doc tells Teddy Martin del Gato was smuggling emeralds inside animals imported from the Amazon, which explains the many deaths Teddy and his father uncovered. Martin blackmailed Doc into removing the emeralds during the animals’ autopsies by threatening his daughter, who belongs to an animal rights organization and was involved with a bombing. Two security vehicles chase Teddy and Doc. Doc encourages Teddy to trust Summer, gives him a flash drive containing all the evidence he gathered against Martin, and tries to distract the security guards. With Summer’s help, Teddy makes it to her father’s office.

The flash drive proves Martin smuggled the emeralds, but he accuses Buck of killing Henry. Teddy uses the clues he collected to explain that Buck must have been the one to release the mamba and the tiger. When the killer tries to flee, Marge knocks him out with a punch. Buck and Martin are arrested, but McCracken decides not to press charges against Doc. Due to Summer’s great disappointment in his thrill rides plan, McCracken promises to abandon it. A month later, Teddy and Summer reunite to watch the hippo Hildegard give birth to Henry’s baby.