Description
Scott Shaw travels to a small town in rural Virginia to search for his daughter, who has been missing after visiting the area with her friends. He gets little help from the locals.
Flashback to six weeks earlier: Jen Shaw, her boyfriend Darius, and couples Adam and Milla, and Gary and Luis, arrive in town to hike the Appalachian Trail. They encounter hostility from locals in the bar, especially from Nate. Jen also meets a strange woman called Edith; with her is a young mute girl, Ruthie.
The friends set off on their hike and despite being warned not to, go off the trail to find an old fort. A huge tree trunk comes crashing down the hill and Gary is crushed to death. Bruised and disoriented, the group gets lost and set up camp for the night. The following day, Milla is missing, as well as their cellphones. They find a plaque dated 1859 commemorating the creation of a group of settlers in the mountains called the "Foundation", who believed the end of the United States was near.
While looking for Milla, Adam is caught in a trap and dragged into a pit. Jen, Darius and Luis come across a barn full of backpacks and clothing, then see Adam trussed to a pole, carried between two men clad in strange costumes and wearing animal skull masks. The friends rush to confront the men, who talk in a language they can't understand. Adam breaks free and manically beats one of them to death while the other escapes. Milla appears and reveals that she went for a bathroom break and hid when she saw the two men. The friends encounter other traps and are surrounded by more masked men. Milla falls into a pit and is impaled on stakes. She is killed with an arrow. Jen, Adam, Darius and Luis are all captured.
The friends are taken to a primitive settlement deep in the forest, the headquarters of the Foundation, and put before a "court". Edith is one of their captors. Morgan, the brother of the man Adam killed, says they killed Milla to spare her a painful lingering death in the spike pit. Morgan testifies how Adam murdered his brother, Samuel. The group is charged with murder. The leader, Venable, sentences Adam to death. The others are sentenced to "darkness". Adam breaks free and holds Ruthie hostage, demanding the release of his friends. Ruthie uses a concealed blade to stab Adam in the leg; he is then executed in front of his friends by Venable, who beats him to death using the log he used to kill Samuel.
Luis tries to flee and Venable blinds him with a hot poker. Jen begs Venable for mercy. Venable agrees, and she and Darius are initiated into the community. Jen reluctantly becomes Venable's sexual partner.
Scott pays a local tracker to take him through the forest. After the tracker and his son are killed by a trap, Scott finds the settlement but is captured. Jen, now married to Venable, shoots her father with an arrow. Venable sentences Scott to "darkness" for trespassing and imprisons him. That night, Jen releases her father, revealing she only shot him so as not to raise suspicion. She tries to get Darius to run away with her and Scott but he refuses to leave. Ruthie helps them escape before Venable and the other cultists pursue them. They discover an underground chamber full of blinded and shambling prisoners, including Luis. Jen kills him out of mercy, and she and Scott flee, killing several cultists, including Edith. They encounter Nate and other armed townsmen who offer to help. The cultists attack them, wounding Jen, but Scott and Jen escape.
Several months later, Jen and her father have returned to their normal lives. Jen visits her stepmother, but finds her in the process of welcoming Venable and Ruthie to the neighborhood. Jen confronts Venable, who notices that she is pregnant with his child. He asks Jen to return with him to the Foundation. Jen agrees on the condition that Venable never again interfere with her family. She, Venable, and Ruthie leave, driving away in a recreational vehicle (RV). As the end credits roll, the RV crashes into a parked car. Jen stabs Venable to death and kills the other cultist. She then takes Ruthie's hand as they walk back towards her family home.
