Plot
In 19th-century Pennsylvania, a small, remote village lives in fear of nameless humanoid creatures, known only as "Those We Do Not Speak Of", that inhabit the surrounding woods. Staffed watchtowers and tall poles with oil lamps line the village perimeter for protection. The color red is banned, as it attracts the creatures.
Following a young villager's death due to illness, Lucius Hunt requests, and is denied, the elders' permission to travel through the woods and retrieve medical supplies from "the towns" to avoid similar tragedies. Later, Lucius's widowed mother, Alice, questions his wanting to visit "the towns", which the elders describe as wicked. The elders appear to have secrets, and each keeps a locked black box containing unknown items. It is believed that as long as villagers avoid the woods, the creatures stay away. Lucius secretly ventures into the woods, though he later tells the elders and claims it was safe. Soon after, skinned animal carcasses appear in the village. One night, the creatures enter the village, leaving red paint splashes on people's doors as a warning.
Elder Edward Walker's daughter Kitty is attracted to Lucius, but he loves Ivy, Kitty's visually impaired and empathic younger sister. Kitty later marries someone else, which allows Ivy and Lucius to become betrothed. Before they can marry, Noah Percy, a young man with an apparent developmental disability, stabs Lucius out of jealousy, seriously wounding him. As the elders consider Noah's fate, he remains locked in a small building.
Edward defies the other elders by sending Ivy, accompanied by two young men, through the forest to retrieve medicine for Lucius, hoping to save his life. Before Ivy leaves, Edward tells her about his wealthy father's murder. He then admits that the creatures are actually the elders disguised as monsters to perpetuate the legend and deter younger members from leaving, but also tells her that folklore suggests that such creatures may truly exist. He then confirms that the skinned animal remains were not part of their plan, that one of the village elders took their lie too far and must be stopped. In the woods, the two boys become frightened and abandon Ivy. She continues on alone and is stalked by a creature, which she tricks into fatally falling into a deep hole as it attacks. Unbeknownst to Ivy, the creature was actually Noah, wearing a costume that he had found hidden under the floorboards. Meanwhile, Edward and his wife Tabitha unlock their box, which contains photos of themselves and the other elders when they were younger. The group is standing outside a modern-day counseling center, revealing that it is actually the late 20th or early 21st century.
Ivy climbs over a high wall. On the other side, she encounters Kevin, a Walker Wildlife Reserve park ranger, who is shocked that she came from the woods. Ivy gives him a list of medicines she must acquire. Kevin gathers the medication without telling his supervisor, nor does he mention Ivy.
It is revealed that Edward, a former history professor, had founded the village over two decades earlier. He had recruited people he met at a grief counseling clinic, hoping to isolate themselves from societal violence. Edward's family fortune funds the wildlife reserve, built the village inside it, and even paid the government to make it a no-fly zone.
Ivy returns to the village with the medication, never seeing the modern world. The elders' boxes are shown to contain mementos and other items from their earlier lives; their voices are heard recalling past traumas. The elders gather around Lucius's bed after learning that Ivy has returned and that a creature, Noah, was killed. Edward comforts Noah's grieving parents by saying that his death will enable them to continue the farce that creatures inhabit the woods.
