Sofi, Liz Dieppa an 18-year-old humble worker, lands a job as a nanny for the children of a wealthy family, a chance that comes through her elder sister Natalia, Alejandra Rodríguez. On her first day, she is introduced to the family’s kids: Gabriel, the eldest and rebellious son, Ceci, the middle and shy daughter, and Bruno, the infant son. While Sofi adapts to her duties with relative ease, she struggles to win their respect, especially from Gabriel, who often mocks and belittles her.
Natalia shares a cautionary tale from her own childhood about Mormo, a child-like demon who haunts spoiled kids whenever anyone invites him into a home. Gabriel, full of bravado, refuses to believe the story and even dares to invite Mormo, but there is no immediate response. Sofi notices that Natalia’s trauma—rooted in memories of their late grandmother who warned them with the same tale in a disturbing way—still lingers, and she senses the legend may carry weight beyond a mere bedtime story.
Soon, strange things begin to unfold: a nutcracker soldier appears seemingly out of nowhere, and a mysterious hoodie-clad figure is seen by Ceci, who insists this is Mormo in disguise. Over the weekend, with the parents away at a wedding, Sofi must stay in the house to look after the children. She becomes more attached to Ceci, who is understandably frightened by the idea of Mormo, even as Gabriel continues to taunt Sofi and dares him to visit again at dinner.
Then Bruno vanishes during a blackout, and Ceci warns that Mormo has taken him, signaling that the danger may be escalating. Sofi asks Mauricio, a security guard, for help, but Mormo closes in and captures him as well. Sofi tells Gabriel and Ceci to flee, but Mormo blocks their escape by playing red lights, green lights and freezing anyone he touches. With Ceci’s help, Sofi unfreezes the others and proposes they play along with Mormo as a way to appease him.
Recalling parts of the tale, Sofi suggests a plan: use a game of hide and seek to draw Mormo’s attention and force him to release Bruno and Mauricio. Ceci stays near the finish line while Sofi and Gabriel search for Mormo. But Mormo cheats by conjuring visions of their relatives and manages to capture Gabriel and Ceci. Grief-stricken yet resolute, Sofi refuses to yield and confronts the demon, ultimately grabbing his nutcracker toy in a move that infuriates him. She offers a deal: if she can return the toy and free the others, Mormo will let them go, but if she fails, she will stay with him forever. Sofi then uses a baby monitor to lure Mormo into a bedroom, freeing Gabriel, Ceci, Bruno, and Mauricio.
The next day, Sofi finds herself spared from dismissal as Gabriel and Ceci stand by her, now clearly bonding with their caregiver. As they walk through the neighborhood, they encounter a spoiled kid who wrecks his toys with a baseball bat, but when he notices Mormo’s nutcracker, it hints that the demon’s next victim could be just around the corner, leaving a lasting sense of unease about what might come next. Throughout, the story unfolds with a restrained, atmospheric tone that centers on Sofi’s courage, the fragile trust forming between her and the children, and the creeping possibility that the haunting tale is more than just a story.
