Four friends on their way to Coachella stop off in Los Angeles to tour true-crime occult sites, only to encounter a mysterious young runaway who puts them on a terrifying path to ultimate horror.
- Elise and her boyfriend Seth, along with Elise's cousin Chloe and Chloe's boyfriend David, become lost in downtown Los Angeles while on a road trip to Coachella. Chloe sees a woman trapped in a nearby building, but is too far away to hear that the woman is shouting at them.
The quartet checks in at the Flower Hotel. Elise specifically requests room 204, where Laney Gore, one of the early sisters of Anton LaVey's Church of Satan, infamously slit her own throat in 1972.
After a day of sightseeing in Hollywood and Santa Monica, the quartet decides to follow Anthony from the occult shop. Anthony leads them to a remote location where they spy an apparent Satanic ritual. Chloe gives away their presence by shouting when it looks like a young woman named Alice is about to be sacrificed as part of the ceremony. The Satanists chase everyone away. Seth loses his phone during the escape.
Alice calls from Seth's phone the next day. She arranges a meeting with Chloe and the others during which she explains that the ritual was not a sacrifice, but was meant to excommunicate her from the cult. Having no place to go, the group invites Alice to stay with them in their hotel room for the night.
Realizing that the hotel room is where Laney Gore killed herself, Alice explains that Laney drew a star on the wall with her blood in order to create a door to Hell, which Alice describes as a state of beautiful confusion. Laney's suicide was supposedly part of a ritual that would bring her to Satan.
Alice leads a summoning ritual with the others. She then draws an inverted pentagram on the wall with the numbers one through five written in slash marks at each point. Alice vomits, urinates on the floor, claims that she will see everyone soon, and suddenly slits her own throat.
Forced to stay in Los Angeles pending a police investigation into Alice's death, David moves everyone to his cousin's empty house. The house ends up vandalized by apparent supernatural activity, including a flock of dead birds littering the pool.
The group returns to the occult store where David angrily confronts Anthony. After taking a punch to the face, Anthony explains that the reason his cult was kicking out Alice was because her Satanic interests were too hardcore for them.
The mysterious vandalism continues. Chloe convinces the others that they should return to Boulder. The car is forced to pull over back in downtown L.A. when Elise becomes violently ill.
Elise finds two slash marks scarred into the side of her body. She enters a port-a-potty and vanishes. Seth hears Elise's voice coming from a nearby building and rushes inside. Chloe and David soon follow.
Chloe and David find Seth vanished with only a bloody trail and three slash marks left behind. David discovers he is marked with four slashes before he becomes separated from Chloe and also disappears.
Trapped in the building, Chloe is tormented by visions of her mutilated friends. Chloe screams at a car outside, realizing she is somehow the person she saw from the street on her first night in the city. Now mysteriously marked with five slashes, Chloe ends up with her mouth sewn shut and her arms cut off as an unseen creature creeps toward her from the shadows.