Jake and his sister, Molly, are looking for a new place to live. When the mice discover Public School 42, they wonder if they should make it their new home. But Jake has scary encounters with an owl and the bully cat Big Gray, and wants to go back to his family. Meanwhile, Molly makes friends with a gentle hamster named Gino (who is also a ghost ) and with Miss Clark's class pets, and wants to stay. Can she convince her brother to live at P.S. 42, even though it is "haunted?"