Baby Modesta lives in a shack on the slopes of Mount Etna with her harsh mother and her older sister Tina. Despite the hunger and poverty in which she lives and her jealousy towards Tina, Modesta grows up with a rebellious spirit and full of life.

Punished by Mother Leonora, Modesta finds herself atoning in a convent cell, but by feigning an illness manages to return to freedom. This does not seem to be enough to get back into Leonora's good graces.

Modesta plays the grieving and devout novice's part to avoid arousing suspicion in Gaia, after Princess Brandiforti and Leonora's mother, who has welcomed her into her villa for a short stay.

Modesta earns the Princess' trust by caring for her son Ippolito, kept segregated because of his condition, aggravated by loneliness. Her place at the villa is still precarious, with the upcoming return to the convent still looming over her.

Modesta secures herself a place in the villa by marrying Ippolito, which draws her away from Cavallina. When Modesta and Cavallina spend some time together, they dream of moving to Catania.

While caring for the ailing princess, Modesta enacts her revenge by gradually poisoning a woman. Modesta realises that the situation has reached a stalemate.