Belly Up is the mystery book written by Stuart Gibbs.
Henry the Hippo is Fun Jungle's mascot. He doesn't like people and is described as being very mean. He enjoys launching poop at visitors. Then about a week after they open, Henry has went belly up on the visitors. Most of the kids don't find out anytime soon. They believe that Henry is sleeping. Teddy goes to Doc and Doc says they will need to perform an examining on Henry to see what killed him.
Teddy sneaks into the examine to see what killed Henry. Doc says that he has holes in his intestine. The holes had killed him. They decide to lie about his death and they say that because people throw food into Henry's mouth and it will make them look bad if the whole world knows that they just let that happen. Teddy however, decides to go on an investigation of his own to see what killed him.
Teddy goes to his mom with the truth about what happened to Henry. He also admits that he snuck into the examination and she is far more concerned with Henry's death that to be mad at Teddy and punish him. She listens to the whole story he has to tell because like Doc, she has a love for animals.
Teddy is concerned with Henry's death and decides to call the police. He talks to the police about the death of Henry the Hippo. The police however, won't do anything simply because Henry is an animal and they can't waste their time on a death that isn't on a human. the police say that animals kill each other all the time and it shouldn't concern Teddy or them. Teddy feels scared and he vows to discover the funny business about Henry's murder.
Teddy finds a heel print in the dirt and tries to find out who it came from. He sees a big crowd standing in a circle around something. He sees its summer Mccracken, the daughter of J.J. Mccraken and the one who came up with the idea of Fun Jungle. Teddy gets past the crowd and meets up with Summer. Everyone is pushing past each other to get her autograph and before Teddy is pushed away he whispers "Henry has been murdered". Summer meets