Thomas, a ten-year-old boy, watches his mother die, powerless to help her. He is in great distress, but reveals nothing to his father, a distant man. His father hires a governess, Mrs. Vernet, whose son Charles is the same age as Thomas. She is a widow, but Charles still dreams of his father's return. While the meeting between the two adults is polite, the two children clash immediately. Thomas's first glance at Charles is fierce, a declaration of war. Who will be the King of the Castle?