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 suspenseful adventure will surely be a hit among Arthur fans.