Betrayed by her classmates and banished to the principal's office for doodling an unflattering sketch of their music teacher, Maxzyne fumes over the unfairness of it all. Could anything worse happen on a Friday afternoon right before the Chicago Festival of Lights parade?

As she nears her dreaded destination, a glance outside reveals a runaway horse and carriage, one wheel trapped in a school bike rack. She races to help, but is it the horse or a mysterious black top hat that entices her to sit in the carriage? There is no turning back, for she is catapulted straight into a misadventure with Rico, an immigrant boy who rides horses in the nearby historic theater.

Together they plan to save the horse, but sharing both ideas and the reins may be difficult when the runaway and the rescue keep shifting in this madcap tale of kids changing hearts, minds, and perhaps even a few grown-up rules along the way.