The cover shows a small hoard of angry hamsters.
Sam Waters and Lexi Blake are best friends. They visit HorrorLand. They go to a restaurant in the theme park called The "Spear-It Cafe". There, they find a cook named Chef Belcher. They have a horrible experience at the restaurant involving shrimp. They run to the Chiller house. Sam who wants a pet gets a insta-grow pet toy and a cell phone, that carries candy. When Sam and Lexi return to their homes with free toys, they get excited when they learn of about the titular shop.
They meet a man named Mr. Fitz, who owns the shop. Many weird things happen for a while to Sam and Lexi. The hamsters turn aggressive. Finally he fights the angry hamsters who have eaten all the candies from his phone. Sam still thinks it is the candy turning them crazy. Then they eat some of his Insta-grow pets and turn huge. Sam also eats a grow pet and they have an epic battle. Sam finally wins, but then discovers that Mr. Fitz was evil. He tells Sam that the Vito Vigor water, that the store sells, is a liquid that turns things evil. He wanted to make the hamsters evil, so he can start a hamster wrestling league. Now he wants the insta grow to make a giant hamster, so he can take over the world. Sam escapes with Lexi's help. Lexi tells him she had ten bottles of Vito-Vigor. She bites Sam.
Then he returned to HorrorLand and Jonathon Chiller traps him there saying, "The horror hasn't started. It will." Then Sam was trapped in HorrorLand—forever.