Elise and her boyfriend Seth, along with Elise's cousin Chloe and her boyfriend David, find themselves lost in the heart of downtown Los Angeles while on a road trip to Coachella. During their wanderings, Chloe spots a woman trapped in a nearby building, but is too far away to realize that the woman is desperately shouting for help.
The group checks into the Flower Hotel, where Elise specifically requests room 204. This particular room holds a dark history; it is the very spot where Laney Gore, one of the early sisters of Anton LaVey's Church of Satan, infamously took her own life in 1972.
After a day filled with sightseeing in Hollywood and Santa Monica, the friends decide to follow Anthony from an occult shop they visited. They find themselves at a remote location, where they stumble upon what appears to be a Satanic ritual. When it seems that a young woman named Alice is about to be sacrificed, Chloe cannot contain herself and inadvertently reveals their presence by shouting. This causes chaos, and the Satanists chase the group away, resulting in Seth losing his phone amidst the frantic escape.
The following day, Alice calls using Seth's phone to set up a meeting with Chloe and the others. She reveals that the ritual they witnessed was not a sacrifice, but rather an excommunication from the cult. With nowhere else to go, the group kindly invites Alice to stay with them in their hotel room for the evening.
As they settle in, Alice shares the eerie history of their room, explaining that Laney drew a star on the wall with her own blood, in a desperate attempt to create a door to Hell. She describes her experience as a state of "beautiful confusion," suggesting that Laney's suicide was a ritualistic act meant to bring her closer to Satan.
Taking the lead, Alice conducts a summoning ritual with their group. She draws an inverted pentagram on the wall, inscribing the numbers one through five in slash marks along its points. The situation quickly spirals out of control; Alice vomits, urinates on the floor, and proclaims that she will “see everyone soon” before tragically slitting her own throat.
As a police investigation into Alice's death unfolds, David relocates the group to his cousin's vacant house. Unfortunately, supernatural disturbances soon plague them, marked by bizarre occurrences, including a pool scattered with dead birds.
Irritated by the bizarre events, David confronts Anthony at the occult shop. After an intense exchange—resulting in David landing a punch—Anthony reveals that Alice's Satanic interests were deemed too extreme for their cult, leading to her banishment.
The incidents escalate, causing Chloe to suggest that they should return to Boulder. However, their car is forced to stop again in downtown Los Angeles when Elise suddenly becomes violently ill. Horrifyingly, Elise discovers two slash marks etched into her skin. When she enters a port-a-potty, she mysteriously vanishes.
Seth hears Elise's voice emanating from a nearby building and rushes inside, followed closely by Chloe and David. They soon find that Seth has disappeared, leaving behind a bloody trail and three additional slash marks. As David realizes he himself has been marked with four slashes, he becomes separated from Chloe and vanishes as well.
Now trapped within the building, Chloe finds herself tormented by horrifying visions of her mutilated friends. In a moment of realization, she screams at a car outside, only to understand that she is the same person she observed from the street on her first night in Los Angeles. Marked with five slashes and facing an unseen beast creeping toward her from the shadows, Chloe's fate becomes terrifyingly uncertain as her mouth is sewn shut and her arms severed.
