Fifteen-year-old Rachel is furious and lonely when her father moves the family to Boston in 1872--especially since she had to sell her beloved horse. But in Boston she finds the Governor's Girl, an injured firehorse, and begins caring for her and thinking about becoming a veterinarian. Then an outbreak of fires causes Rachel to question the ethics of her journalist father, and when the horses who pull the fire engines fall ill, the danger escalates. In a dramatic climax, the Great Boston Fire of 1872 is brought to life with cinematic vividness, and Rachel proves her grit and determination to make something of herself.