Malcolm, a smaller than average rat, loves life at McKenna School and the secret society of classroom pets that keep children out of trouble, but when Aggy the iguana disappears Malcolm must use all of his ratty persistence to prove his innocence and save her.
Tyler is a bully who enjoys frightening other students, but when his only friend, his class's pet rat, gets out of her cage he needs the help of a human friend, and fast.
When a rare coin and a strange code are uncovered in McKenna School, Malcolm and the other classroom pets of the Midnight Academy take on their most challenging assignment yet and, through their investigations, they just might save the school from closing.