Mrs. Jorstad kills her cultist husband on a small Norwegian fishing island. Mrs. Jorstad then escapes to America with her young son Isaac.25 years later, Mrs. Jorstad's son Isaac Pickman returns to Norway with his pregnant wife Emma to claim the inheritance on his childhood home. Emma begins having recurring nightmares involving a cult, aquatic monsters, her unborn child, and her husband descending into madness.Isaac gets into an altercation at a bar when locals Gunnar and Ledvor take issue with Isaac being American. When they discover Isaac is actually a Jorstad, the men suddenly become welcoming.Local sheriff Renate visits Isaac to ask about his father's death. Isaac tells Renate that his mother claimed her husband left them. Renate reveals she believes Mrs. Jorstad killed Isaac's father before fleeing to America with Isaac.Renate invites Isaac and Emma to her house for dinner. Isaac and Emma note an odd effigy outside, which Renate explains is a customary tribute to her late husband. Isaac and Emma meet Renate's daughter Astrid, who exchanges strange stares with Isaac. Over dinner, Renate discusses 'The Slumbering One,' an ancient aquatic deity integral to local folklore.Renate invites Isaac and Emma to an annual sacrament to see local customs firsthand. Isaac unexpectedly joins Renate's robed cult in the water for their ceremony. After reciting a pledge to The Slumbering One and being baptized during the ritual, Isaac's behavior begins growing worrisome for Emma.Upset after Emma jokingly insults what she witnessed, Isaac later goes to the water alone. Astrid rises from the sea naked. Astrid entrances Isaac as they have a cryptic conversation.Emma and Isaac meet with realtor Matias about selling the house. Convinced by Gunnar and Ledvor that he has found his true home, Isaac surprises Emma by revealing he refuses to let them leave. Emma tells Isaac he has lost his mind. When their argument suddenly turns violent, Emma knocks Isaac unconscious to escape.After the ferryman refuses to take her to the mainland, Emma goes to Renate for help. Emma is surprised to find Isaac at Renate's house. Emma falls unconscious after unknowingly drinking water that Renate drugged.Emma wakes up tied to an altar surrounded by robed cultists. Isaac raises a sword to stab his wife in her pregnant stomach. Renate suddenly has the cultists take Isaac captive instead. Renate reveals Isaac was meant to be their sacrifice until he escaped with his mother 25 years ago. The cult decapitates Isaac. As Isaac's body is set into the water for The Slumbering One, Renate assures Emma she will get used to the ritual.(Thanks to Culture Crypt)