Patricia Alvarez is introduced as the single mother of two boys, Carlos and Tomas, and had been familiar with the film's main protagonist, social worker Anna Tate-Garcia, as she had been on call to the Alvarez house on a near regular basis. The early scenes of the film had Anna arrive at the house with a police officer, as Carlos and Tomas had been missing days at school, and there were suspicions of child abuse.
Once Anna entered said house, she is confronted by Patricia, who refused to answer Anna's questions regarding the whereabouts of her sons and also shouted at her to not open a locked door she was close to. When Anna approached the door anyway, Patricia turned heel and attacked her, with the latter breaking free from the psychotic villainess' attack and opening the door to find Carlos and Tomas inside. Anna noticed bruises on the boys' arms, believing them to be caused by Patricia, only for the boys to tell them that their mother was not responsible.
Later on, Anna is on call after it was reported that the boys had drowned in a river, and Patricia was shown being handcuffed and arrested by the police, as she was suspected of killing them. The maniacal Patricia lashed out at Anna and blamed her for her sons' deaths, as she stated that she was protecting them from La Llorona, an evil spirit who approaches children and drowns them, with Carlos and Tomas being her latest victims. A reluctant Anna later visited Patricia in prison after she refused to cooperate with the police, with the latter continuing to blame the former for the loss of her sons while also showing that she was bruised and touched by La Llorona just like they had been. Anna's visit was due to La Llorona pursuing her children (son Chris and daughter Samantha), and as further proof of Patricia's unhinged personality, the villainess stated that she prayed not to God, but to La Llorona, wanting her to go after Anna's children so her sons could return to her—indicating that she had sworn revenge on the protagonist.
Patricia ended up being released due to a lack of evidence and having a solid alibi for the time of Carlos and Tomas' murders, but in the film's climax, the evil Patricia armed herself with a gun and appeared at Anna's house in a white outfit, doing so after former priest Rafael Olvera's assisted the Garcia family in dealing with La Llorona. The deranged and vengeful madwoman took Chris and Samantha hostage and (non-fatally) shot Rafael before calling out to La Llorona, requesting that she take Anna's kids in exchange for giving her sons back to her. When her two would-be indirect victims fled her grasp, she resorted to allowing La Llorona inside by deliberately breaking the protective line of fire tree seeds, which resulted in Anna being locked in the basement while the malevolent spirit entered the house and went after her children. After hearing the mayhem in the attic and Anna's pleas, Patricia had second thoughts and freed her, with the former killing La Llorona with a fire tree cross, and it can be assumed that the latter was arrested offscreen for her crimes.
- Patricia Velasquez previously portrayed Anck-Su-Namun in The Mummy and The Mummy Returns.