Evan, a college student, embarks on a journey to Joshua Tree, California to reconnect with his older brother, Peyton. This trip is set as a chance for the two brothers to strengthen their bond while exploring the scenic desert landscapes. During their adventure, they encounter a lively group of nine vacationers, including photographer Zoe and her friends Camille, Tori, Vanessa, Haley, Nico, Max, Sam, and Bryan. As the day unfolds, Evan and Zoe share an unexpected connection, which deepens their bond.
That night, Peyton encourages Evan to join the group at their rental house, where they spend the evening indulging in drinks and sharing spooky tales. When it’s Evan's turn to contribute to the storytelling, he recounts a legend of a monster called the Hisji—a malevolent entity that cannot be named five times. The group's reaction is largely dismissive, yet Evan and Zoe’s adventures take a turn when they hear strange noises and witness an unidentified figure while relaxing in a hot tub, leading to a night of intimate surprises.
As dawn breaks, Evan notices a mysterious blonde girl at their rental house. His curiosity leads him to explore a nearby dilapidated structure, where he discovers a five-pointed star within a circle etched into the wall. This unsettling find is interrupted by Zoe's unexpected appearance. The group's itinerary includes a trip to a nearby hill overlooking the park. However, tension escalates when Camille mistakenly believes she sees Bryan in the kitchen, though he is spotted outside moments later, and the blonde girl seems to vanish from sight.
During their visit to the hill, Zoe experiences an inexplicable compulsion to leap off a cliff, subsequently suffering a broken ankle with no memory of the event. This incident heightens the group's concerns when they later encounter Peyton, who returns to pick up Evan. Despite Peyton's offer to leave with him, Evan chooses to stay. Engaging in a game of "Never Have I Ever," the atmosphere shifts dramatically when another Sam appears from the other room just as the lights flicker off, triggering a wave of paranoia among the group.
As suspense builds, Evan recalls details about the Hisji he had previously shared and investigates further, discovering the monster preys on groups of five and has been tied to a missing person case from 2007. He is alarmed to find the same symbol he earlier discovered in police reports. When Evan finds Zoe outside, she cryptically tells him she is going to the mines with Max, which raises alarm bells. Rushing inside, he finds that only five people remain in the house, compelling him to return with Camille.
Upon their return, they are met with chaos: Tori, Sam, Haley, and Bryan have vanished, and Zoe outside exhibits unsettling behavior, revealing that the Hisji has taken on her form. In a horrifying twist, the creature drives Vanessa to harm herself, leading the group into a frantic panic as the Hisji reveals its true monstrous shape. It attempts to breach the house, imitating victims, but ultimately succumbs to fast-paced horror as Camille, Max, Vanessa, and Nico are forced towards tragic ends. In a state of desperation, Evan reaches out to Peyton with a voicemail, but it is too late; the Hisji manifests before him in Zoe's guise.
The following day, Peyton returns to the house, only to find remnants of the previous night’s horror intact. Just as he prepares to listen to Evan's voicemail, an seemingly unharmed Evan surfaces, apologizing for his prior actions. As they leave the eerie desert behind, Peyton reassures Evan, promising to introduce him to his friends, leaving the future uncertain yet tinged with hope.
