At a shopping mall, a man suddenly dies on the sidewalk. At home, his family is wondering what has become of him. Dad is a watchmaker who repairs watches at the street market, and the family's sole means of support.
As Dad has not appeared for the day's work, Alfredo and Julián head to the market. Julián gets into a fight with a customer who claims that his watch is three weeks overdue. The woman who runs the market appears and tells the boys to get out; the rent for their booth at the market is three weeks in arrears.
When the boys arrive at home, their sister Sabina enters in a state of shock and announces that their father has died. Their mother, Patricia, locks herself in her room; the children wonder who is going to provide for the family now—specifically, their meals: this family performs cannibalistic rituals.
In a morgue, Tito the coroner and the director of the funeral home bring in Octavio and Owen, two police detectives. The coroner shows them a finger in a jar: it was pulled from Dad's stomach. The detectives are asked to solve this cold case. Initially, they resist, but as the film continues, they become more interested in the fame that will come with solving it.
Alfredo and Julián attempt to kidnap a homeless child from under a bridge, but are chased off by the other children. Next, they attempt to kidnap a prostitute, who also resists; Julián punches and stuffs her into the back seat of their car.
Back at home, the boys tie the prostitute to the kitchen table. Patricia comes in and beats the woman to death with a shovel, claiming that Alfredo does not know what he is doing, and that prostitutes are not appropriate for the ritual. Alfredo runs out while Julián and Sabina wrap the dead woman in a sheet. Julián and Patricia take the prostitute back to the corner where the boys picked her up and dump her in front of the other street workers. Patricia tells the women to leave her sons alone. The prostitutes report the incident to detectives Octavio and Owen.
Alfredo goes looking for another potential meal; he follows a group of young men to a gay bar, and begins to seduce one of them. At the same time, Patricia is having sex with a cab driver, in his car, in order to entice him to her home. Alfredo brings the young man from the bar home with him, but Julián says he will not eat a homosexual man. As Alfredo and Julián argue the point, the cab driver comes down from their mother's room. Alfredo's prey escapes while Patricia beats the older man over the head with a shovel and the family later kills him.
As Sabina and Patricia prepare the man for eating, Alfredo and Julián chase after the gay boy. The boy runs to a fast food stand and asks the police to protect him. Detectives Octavio and Owen hear the call over their police radio and head to the scene. They decline to call for backup, as they want to keep the glory of the collar for themselves.
Detective Octavio stops Alfredo and Julián in an alley, holding them at gunpoint, but is shot by a uniformed officer who mistakes Octavio for a criminal. Detective Owen discovers Sabina and Patricia preparing their meal in a ritualistic fashion, but the women kill him. Alfredo and Julián arrive home; Patricia insists on completing the ritual, but Alfredo drags her away to escape over the rooftops.
The police break into the family's home and Julián shoots several of them before the family manages to hide upstairs. Their mother says that one must survive to carry on the ritual and flees to the rooftop. The prostitutes shown earlier in the film see her escaping and pursue her.
Meanwhile, Alfredo bites Sabina's neck. Julián, thinking Alfredo's attempting to eat Sabina, shoots Alfredo. The police kill Julián and take Sabina away in an ambulance, believing that she is a surviving victim. The next morning Patricia's body is discovered in a playground, beaten to death.
After escaping from the hospital, Sabina watches a young man in the market, intent on her next meal.
The family's attempts to continue their ritualistic cannibalism after the patriarch's death lead to violent confrontations with both their intended victims and law enforcement, culminating in deadly consequences.
The conclusion lays bare the destructive impact of family tradition and grief, escalating from internal strife to inevitable violence with outsiders. By holding tightly to their rituals, the family members doom themselves, exposing the corrosive power of inherited roles and obsessions in the face of a society that will not tolerate their secrets.