In 1673 Mexico, a family plays in a field, and the youngest son gives his mother a necklace, who says she will treasure the item forever. The boy goes on a hike a while later and finds his mother violently drowning his brother in a stream. Horrified, he runs, but his mother catches him and drowns him too.
300 years later, in 1973, Los Angeles, caseworker Anna Tate-Garcia investigates the truancy of client Patricia Alvarez’s two children. Arriving at Patricia’s house for a welfare check, she finds the children locked behind a door. Patricia attacks her and is taken away by the police. Patricia’s sons, Carlos and Tomas, tell Anna to keep them in the room, so they are protected. Ignoring their warnings, she takes them to the child-services shelter. There, Tomas sleepwalks, and Carlos follows him until both boys see a woman in a white dress who attacks them.
The boys are found drowned in a river, and Anna is called out to the scene. She brings her own children, Chris and Sam, and they stay in the car while she investigates. She hears Patricia, accused of her sons’ murders, screaming that it was Anna’s fault for taking her sons and that Patricia had tried to stop the malevolent force of “La Llorona.