Lilly and her friends have a substitute teacher named Mr. Wulf who takes them on an overnight field trip. Lilly jokes that he looks like a werewolf, and is surprised when her friends take her seriously.
On the bus, her best friend Minna won't sit with her. When they have to go on a moonlit walk, no one wants to go because they're afraid of their teacher. When Mr. Wulf finally hears about the rumour, his feelings are hurt, badly. Lilly has to do her best to make things better.
Lilly in the Middle is a touching story about a thoughtless rumour that gets out of control, and about one girl's efforts to overcome it.