After Lee is taken away by the police, Shelby confronts Matt about having seen him having sex with the woodland witch. Matt breaks down swears he doesn't remember, and Shelby eventually believes him. She realizes that he wasn't culpable for what happened.
Shelby goes to take a shower and is attaked by the Pig Man wielding a knife. He pursues Matt and Shelby through the house, eventually cornering them. Elias Cunningham appears, hitting the creature with an axe. The creature gets back up, unfazed, but Elias banishes it by saying Croatoan, though he warns them that the Pig Man will be back.
Elias pours himself a drink and explains the situation to Matt and Shelby. He owned the house, though he didn't live there, preventing anyone else from acquiring it -- until he lost it for owing taxes, and Matt and Shelby bought the house at auction. He also explains that "Croatoan" was a word used as a message so that the other colonists could find the Roanoke colony, but that it's a word of dark power.
Matt tries to kick Elias out, but Elias stops him, showing them his research. Over the years, people living in the house vanished or were murdered within the same lunar cycle every year (until Elias took ownership of the house) -- like the Chen family in 1973.
The Chens, an immigrant family, were stalked by the Pig Man. They tried to call upon their ancestors for protection, but regardless the family was killed by the Butcher once the Dying Grass Moon arrived. Shelby looks over his research, realizing that the disappearances and deaths date back to the 1700s.
Elias confirms that the ghosts of the murderous nurses found him when he was hiding in the forest and told him the story of their death -- they were captured by the Butcher's people because they didn't leave the house. She had one's arms pulled out and chopped the other's head off, leaving them to bleed to death.
Elias tells them that the cycle is starting that night so they need to leave immediately. Shelby and Matt refuse to leave without Flora. When they mention Priscilla's name, Elias recognizes it and leads them to where Priscilla likes to hang out on the periphery of the land with the other ghosts of people killed by the Butcher, who are all bound to the land for some unknown reason.
On the way to find Flora, the group encounters the woodland creature. Elias tells them to ignore it, but Shelby is driven to chase it through the woods. Eventually, she loses the creature but stumbles upon the ghosts. She attempts to banish them with "Croatoan," but it doesn't work because the first quarter moon has already begun.
They find Flora among the ghosts. Elias approaches Priscilla, trying to convince her to let Flora go. Before anything can happen, a hunting horn sounds and Elias is suddenly struck dead by the colonists' arrows. Shelby and Matt escape, without Flora, and make it back to the house where they're greeted by Cricket.
Cricket insists that Flora is not dead but criticizes the Millers for going against the agreement to leave the land. He decides to leave the house, so he can confront the Butcher again and get a sense of what they're up against and the colonists' weaknesses. Hours later, Cricket comes back shaken, having met the woodland creature -- the "bitch with the real power."
Cricket realizes that the creature, Scathach, is behind the Butcher's power and that her own power grows with each cycle of the moon but her womanly "needs" also increase. Cricket explains to the Millers that he offered Scathach Matt in exchange for information. Scathach showed Cricket that the Roanoke settlers came to the land where the Millers' house stands. In order to continue their bountiful harvest, they practiced human sacrifice.
In the past, the Butcher's son speaks out against her for having fallen prey to the "evil witch." He begs her to allow them to return the way they came and to go back to England. The creature convinces the Butcher to sacrifice the entire group of colonists, releasing the power of the blood moon and guaranteeing the colonists' souls enslaved to the Butcher for eternity.
The Butcher pretends to be contrite and to repent, but she actually poisons the colonists (including her son) and slaughters them all. Then, the Butcher willingly allows Scathach to kill her, binding them all to the land.
In the present, Cricket explains that on the anniversary of the slaughter, the spirits become lethal. He also notes that the witch allowed him to see a spell to be able to put the Butcher and colonists down for good. He leaves to go back to his room and gather supplies.
On the way to the hotel, Flora darts in front of the car. Cricket chases after her, disappearing for hours. Shelby and Matt wait for Cricket back at the house and begin to worry. While Shelby sleeps that night, Matt is drawn to Scathach outside of the house. They have sex with Matt under her spell, during which Scathach opens up herself (and her history) to Matt.
Scathach was once an English girl who stowed away on a ship to America. Everyone on the ship died, and she was set to be burned at the stake becaues the settlers believed it was her fault that the sailors had died. She kills the soldiers keeping her captive and escapes into the wild, becoming a powerful witch. Matt believes she told him all of this because she wanted him to understand her and join her -- which he admits he would have.
Mid-sex, Matt hears Shelby screaming for him as the colonist ghosts walk up to the house. He leaves Scathach behind moaning and screaming for him. At the house, he finds Flora about to be killed by the Butcher. Priscilla intervenes and the family is able to escape into the house. From inside, Matt and Shelby watch as a captive Cricket is violently disemboweled by the Butcher.