Maddie is a 15-year-old girl who has lived in her grandparents' country estate in England, ever since her parents died. Her older sister, Louisa, also lives with them--but Theo, their brother is fighting in the Great War (WWII).
The main plot of the book begins when Theo suddenly returns from the war--what a wonderful surprise for the family! It has been so many years and Theo has changed so much. He awkwardly tries fitting in with their life at Sefton Park. However, most of the time, Theo is out in the stable with the horses. Because of him, Maddie takes the leap and finally shows an interest in horses, just like what her grandparents had wanted her to do for so long.
She slowly becomes more and more attached to her brother until she uncovers something he has been hiding from the family. It is intriguing and astonishing--it even caught me by surprise! However, by the time Maddie finds out Theo's secret, if she tells everyone it will wreck all the horse riding plans that she and her brother had. How much farther will she go without telling? What kind of trouble is it going to cost her?
"Heart of Fire" is a excellent story, and revolves a lot around horses. So, if you're a horse fanatic and love historical fiction, I'm sure this is the book for you.