Locked in the Library!, Book 6 by Marc Brown

After Arthur calls Francine a marshmallow, she refuses to speak to him. Then Mr. Ratburn pairs them up for a homework project. They reluctantly go to the library for research-and find themselves locked in once the library closes. Will Arthur and Francine set aside their differences and work together to find a way out? In chapter-book format, for children who are ready to read on their own, this supenseful adventure will surely be a hit among Arthur fans.