Rosalma is born into a family of curanderos, spiritual healers who use ofrendas (offerings) to cure the sick. As a young maiden, she marries Manuel and soon discovers that she is unable to bear children of her own. Having a child is the only way that curanderos can pass their magical powers, so Rosalma resolves to cure herself through magic. She asks her father, a great renowned curandero, for advice, but she is turned away when he reveals that creating a life is a dark and forbidden act. Determined, Rosalma rummages through her father’s ancient books and private notes and discovers the solution. In order to create life, she must make three grave sacrifices: her true love, her congregation, and a gift that only a mother can give.
One cold, rainy day, some time later, Manuel is out fixing a leak on their roof and consequently comes down with pneumonia. Rosalma can heal him but finds her first opportunity to make her first sacrifice. She lets Manuel die in her arms as she captures his last breath in a vial. Uneased by the constant memories of her husband, Rosalma decides to move to a distant town and lays roots in this new community. There, she earns the trust of her congregation by healing the sick and tending to small children. She makes such an impact that the community puts together a ceremonious fiesta where they reveal to Rosalma that the newly erected church will be dedicated in her name. The community members revel and dance in happiness at the fiesta. Rosalma is beyond touched by the sentiment of her congregation that she gives them a present of her own: magical sparklers that last for hours. The children are thrilled and run about with the sparklers in hand.
Soon, however, the celebration comes to a halt when a tent catches fire from one of the sparklers. The flames quickly build and spread as heavy black smoke billows. The community members run and scream for safety. After a struggle, the community men manage to put the fire out. Beatriz, a community member who sells flowers for a living, approaches Rosalma in a panic. She cradles her son, Mateo, in her chest as he rocks back and forth in an effort to catch his breath. The smoke from the fire has caused him to have one of his worst asthma attacks yet. He needs serious and immediate help, so Rosalma instructs Beatriz to fetch two dozen of her most beautiful roses tied in a yellow bow as an offering while she takes the boy to her home. There, Rosalma lays the boy on the floor and begins to perform a ritualistic magic as Beatriz arrives with the roses. As Beatriz waits outside in tears, Rosalma stops her ritual when she sees the opportunity to make her second sacrifice: her congregation. As the boy’s heart takes its last beat, Rosalma captures his essence in a vial. A few moments later, Rosalma opens her door and faces Beatriz. She tells her that she was unable to save Mateo. Beatriz rushes into the house and breaks down in tears as she hugs her dead son.
Days later, the community holds a wake and Rosalma prepares the body for burial. After the boy is buried, Rosalma goes back to her home anxious to perform her last and final sacrifice, a gift only she can give: her magic. She goes into a trance and gives up her magic, collecting it in a large vial. Now that she has everything that she needs to create a child of her own, Rosalma creates the elixir to create life. She then takes the covers off her bed where Beatriz’s son lies still. Never burying the child, Rosalma forces the elixir down his throat and after a few fearful moments the dead boy rises. He is not the same Mateo, but a new boy with distinctive features of Rosalma and Manuel. Rosalma holds the confused and tired boy in her arms and names him Diego.
As the community grieves for the loss of Mateo, Rosalma takes a trip to a nearby town under the guise that someone has requested her help. Under the stealth of night, Rosalma hides Diego and takes him with her. When she return to her community, she announces to everyone that she has adopted a son, her Diego, a boy orphaned by the “person” Rosalma was unable to save in the nearby town. Rosalma begins her new life with Diego, slowly teaching him how to use his magic as a curandero. The community members still approach Rosalma with their ailments, but they are unaware that Rosalma no longer possesses her magic. Rosalma needs the boy to focus, but all he wants to do is conjure and play with fire, of which he is prohibited from doing for its inherent danger.
Upset that Rosalma keeps him at arm’s length, the boy schemes and carries out a series of disquieting acts of hate against his community. He burns the feet of a neighbor’s chickens, he lights a dog’s tail on fire, and he burns a batch of freshly grown flowers to a pulp. While the boy refuses to learn how to harness his powers, Rosalma has to keep making excuses for not being able to help the sick in her community. Meanwhile, and unbeknownst to Rosalma, the parents of the community forbid their children from playing with Diego, further isolating him and fueling his hatred toward the entire community. The children of the community, however, are unaware of Diego’s actions, and soon Diego secretly befriends and gains the trust of a girl named Maria.
About the same age, Maria and Diego play in secret and enjoy each other’s company. Diego, scheming all along, finds an opportunity to hurt Maria. Behind the church alley, Diego puts Maria in a trance and makes her burn her own forearm with a stick he lights on fire. Shocked by the pain, Maria awakens from her trance and realizes what Diego has done to her. Scared, panicked, and crying, she runs away, yelling that she will never see him again. Upset at the turn of events, Diego’s hatred grows. He sees the church he is standing beside, smirks, and lights a bushel of dried grass nearby. The fire quickly begins to form.
Meanwhile, Lita, a community member, had been visiting Rosalma in her home to be treated for a bout of bad stomach cramps. Rosalma performs a familiar act. She rubs Lita’s body with an egg while she whispers a prayer and applies a sweet oil all over her back. Lita rises at the end of the ritual, but she is not healed. Lita is confused. She has visited Rosalma multiple times with the same ailment, and she has been cured every time. Lita asks Rosalma if something is wrong. Rosalma is filled with trepidation from the fear that her secret might be exposed. Considering Rosalma a close friend, Lita uses the opportunity to try to talk more about Diego. She also shares how the parents of the community have come together to forbid their children from playing with the boy. Rosalma is taken aback, but Lita begs Rosalma to tell her more about Diego, hoping that any information might help ease the parents’ minds.
In the moment, Rosalma lies and expands on her original story, but Lita is unconvinced about the details. Lita grows suspicious and leaves Rosalma’s house confused and on edge. On her way home, she’s passing by the church right when Diego is lighting the dry grass on fire. While she catches him in the act, the church quickly lights ablaze and Diego disappears in the smoke. Soon, the church is engulfed in fire. The community runs toward the church to fight the fire, reliving the horror of the day of the fiesta. This time, there is no doubt that Diego is a menace to the community. They are able to put the fire out, but the church is completely demolished.
Diego runs home in a coughing fit as he finds Rosalma buried in tears. “There will be people next,” he simply states as members of the community arrive at her door. Scared for the safety of her child, Rosalma cradles Diego as she opens the door. The community members yell in anger, condemning Diego for the fire. Diego’s cough escalates into an asthma attack, and he rocks himself back and forth to find comfort. Beatriz takes note of Diego and the way he swayed under Rosalma’s embrace. Rosalma closes her door in anger, ordering everyone to leave her and her precious son alone.
The community dissipates, but Beatriz confides in Juan, a prominent leader of the community and Maria’s father, about a suspicion that has just occurred to her. Together, they run to the community graveyard where they begin to exhume Mateo’s coffin. When they’ve succeeded, they open the coffin to find two big bushels of dried roses, tied together with a yellow bow. Beatriz and Juan quickly return to town to confront Rosalma, gathering members of the community along the way. They divulge their findings, and the crowd grows raucous. They arrive at Rosalma’s house and pound at her door and windows as they scream hostile threats and shout for answers. As Diego never learned how to use his powers, Rosalma has to coach him in order to cure himself. The cacophony outside intensifies, and Rosalma must contend with what to do: save a community she has betrayed or the dying boy cradled in her arms. End.