Mad Shadows explores the psychology of a single family: Patrice, the beautiful and narcissistic son; his ugly and malicious sister, Isabelle-Marie; and Louise, their vain and uncomprehending mother.

As they return home, their daily activities reveal even more of their living situation with one another, as Isabelle-Marie is the Cinderella of the family, works hard, and is neglected.

Isabelle-Marie continues her distaste for her brother, and as her mother is no longer there to support Patrice, she takes the opportunity to let him starve to release her anger and jealously towards him.

As Isabelle-Marie becomes more upbeat, she learns to care for Patrice and meets her lover, Michael, whom she convinces to love her by lying about her beauty.

Both children's stories end in despair, as Michael eventually regains his vision and comes to terms with the ugliness of Isabelle-Marie and consequently their newborn child, Anne.

Louise, who has slowly been cracking under the loss of her beautiful child and the control and eventual death of her husband, is lost in the fire.