Mom lets Rosalyn in. She tells Rosalyn that Calvin is upstairs hiding from her, so she may have an easy evening. Rosalyn says that would be good, since she has to study for a big test tomorrow. Upstairs, Calvin and Hobbes are listening around the corner. As Hobbes rubs his paws together, and Calvin puts on an evil smile, he declares that tonight is "The Revenge of the Baby Sat".