Ten-year-old twins Jimmy and Stella start a campaign to save their dying small town (population 49) by restoring the amazing hippomobile, an old-fashioned vehicle made out of a horse wagon.

The oldest Marriss brother, fourteen-year-old Dewey, attempts to be the "embodiment of responsibility" as he juggles the management of the family's bicycle repair business while sharing the household and farm duties with his siblings after a sudden energy crisis strands their parents far from home.