Three‑year‑old little girl Mopsy, transported to another world, possesses extraordinary strength. Amid royal upheaval, she chooses to follow the gravely injured young prince Edmund to Frostmarch, a remote, poor fiefdom in the northern lands. Faced with perils along the journey, Mopsy protects her companions with childlike purity, courage and kindness and meets diverse allies. Side by side, they confront numerous crises, build a home in the harsh north, comfort one another, and pursue their own hope and belonging.