Leonarda Cianciullio is a mature Neapolitan woman who moves to their new house in a Northern Italian city that her husband, Rosario, bought. Michele is their eldest son. Rosario falls paralyzed, and Tina, their mentally retardant servant, used to take care of them. Leo starts to manage a lotto box office. Berta had been a spinster her entire life and had come to her to check her lottery. Berta also confesses that she has decided to go to America to be with her husband. Leo says that she had thirteen children. Still, all except one died during abortion or within a few months of birth. She has a pathological fondness for Michele, her sole survivor, and believes she has stolen him from Death by bargaining with it.
Leo goes to church with her friends Lisa and Berta. Leo notices Michele standing with a young lady, Sandra, a dance teacher. When Leo discovers
Sandra lives with the singer Stella; she visits her place, sneaks into Sandra’s room, and collects her hair and her father’s photo. The same night, she teaches Tina how to cut the meat, takes the lamb’s heart, and places it inside a jar along with the photo and hair she took as a practice of death offering.
On one fine day, she invites their church father, Onorio, his sister Maria, Palma, Stella, Lisa, and Berta to throw a send-off party for Berta. Maria convinces Berta to send cards and letters to her loved ones once she reaches America and suggests that she mail them a letter assuring them that everything is okay. Leo visits her son Michele and finds him in a hotel room with Sandra, who is naked. She gets angry and asks him to come with her. But Michele refuses to do so.
Berta came to see Leo one more time as she prepared to go. Leo uses the opportunity and decapitates Berta’s head with an ax, dragging the body into a closet. She splits the body into nine pieces and boils them. She also adds caustic soda to it. The next day, she crushes all of Berta’s bones into powder with the help of innocent Tina. Michelle takes Leo to Stella’s singing night. When he notices Sandra there, he leaves his mom and starts dancing with her, which irritates Leo. As a result of her practice, Sandra’s father passed away the same night.
When her friends visit the following day, she feeds them cookies made from Berta's bones. For her neighbors, Leo's soap has a certain mystique. They decide it's suspicious, pursue her, and make an effort to inquire into her. Even after Sandra's father has passed away, Leo continues to be upset by her timely arrival. Leo sends Tina to Michele's room naked to divert his attention away from Sandra. Michele is unhappy with Tina's behavior, advises her that this is improper, and sends her back to her room. Like Berta before her, Lisa paid a visit to Leo. In addition, Lisa received tainted wine, and she was killed with an ax. Lisa's body accepted the same care. Neighbors become suspicious when they find black smoke emitting from Leo’s kitchen exhaust when she makes soap. The next day, she visits the bank and draws 3,000 lira using Lisa’s name.
When neighbors see Maria, they give her the soap and complain that they couldn't sleep well after purchasing it. And they feel the presence of the devil inside. Maria gets angry when she feels they have the wrong opinion about her friend Leo. Sandra comes to their home for lunch, and Tina tries to show her the kitchen and jars filled with blood and crushed bones. Unfortunately, Leo comes there and warns her not to do so. One night, church priest Onorio asks for help from Leo to see his sister Maria, who feels suddenly ill. Onorio mentions that Maria was lately blabbering something about the soap. When Leo checks the bathroom, she finds Berta’s ring in the soap.
She takes that out and has a conversation with Maria. Leo then comes clean about killing Lisa and Berta. She also claims that seven kilograms of caustic soda, which she had bought to make soap, were added to the kettle with the fragments. Soon after listening, Maria passed away.
The next day, the new chief investigates Breta and Lisa’s missing case with Leo. He couldn’t take any action without proper evidence. The widow Stella, a former soprano, was Leo's third and last victim. Stella consented and made her final trip to see Leo. The murder followed the same pattern as the first two. Stella's body melted to create soap, unlike the bodies of the prior two victims. Leo reportedly received 50,000 lire, several diamonds, and government bonds from Stella. Even the clothing and shoes of the victim were sold by her.
To be prepared for the Second World War, Michele goes to enlist in the Royal Italian Army. She is unwilling to sell him to the army or another woman. When her son's summons to active duty arrived, Lea wanted to increase the number of sacrifices to bring him home. She was determined to keep him safe at all costs and concluded that this meant making sacrifices for other people. This time, she was trying to sacrifice a mute servant and Michele's girlfriend. She was quickly stopped and caught by the police.
