Foil
Explanation and Analysis—Agnes and Joan:

O'Farrell uses the contrast between Agnes and her stepmother Joan as a classic example of character foils. Agnes is intuitive, attuned to nature, and gifted with insight. She moves through the world guided by instinct, reading energy from people's hands and trusting her connection to the natural and spiritual realms. Joan, by contrast, is rigid, domestic, and domineering, defined by social conformity and the desire for control.