Nick Eliot, a young writer, moves into a guest house on the property of a wealthy family. He soon befriends their 14-year-old daughter, Darian. Initially, Darian appears to be a sweet, intelligent, and charming teen who is eager to spend time with Nick. As they grow closer, Nick begins to notice that Darian's interest in him goes beyond that of a typical friendship. She starts to make romantic overtures towards him, which he initially brushes off as innocent crush behavior.

However, Darian's behavior rapidly escalates from harmless infatuation to obsessive and dangerous. She becomes increasingly manipulative and deceptive, resorting to drastic measures to ensure that Nick remains in her life. As she becomes more unhinged, Nick finds his professional and personal life unraveling under the weight of Darian's relentless advances. He tries to distance himself from her, but Darian's actions start to have alarming consequences.