William the hippo and his friends live on 5th Avenue, New York, inside the Metropolitan Museum of Art. At night, when the museum is closed and all the visitors have gone home, their adventures begin. A special exhibition is about to open, and everyone is excited to see the amazing exhibits from all over the world. However, the boxes holding the exhibits are locked with puzzles that need to be solved. The curators are struggling to figure them out - it's up to you to help William and his friends travel through the museum, solve the puzzles, and save the exhibition!