10-year-old Cécile has a hard time adapting to life in the village her mother and she just returned to. The arrival of a travelling circus finally offers her some distraction. Everyone rushes to see Poly, the flagship pony. When Cécile finds out its owner Brancalou mistreats the animal, she saves Poly! Hiding her new pony friend from the adults, Cecile finds unexpected allies in the mysterious Victor and the kids of the village. With Brancalou on their tracks, Cecile and Poly embark on an adventure full of danger and surprises..