Here's a full plot summary:
Rebecca is excited to start college and is looking forward to her new life in the dorms. Her roommate, Sara (Leighton Meester), seems initially friendly and welcoming. However, Sara's behavior gradually becomes increasingly possessive and controlling.
Sara's obsession with Rebecca grows rapidly. She starts making Rebecca's decisions for her, interfering with her social life, and even sabotaging her relationships. This includes preventing Rebecca from meeting other people, manipulating her friends, and making sure Rebecca spends all her time with her.
Rebecca starts noticing red flags and growing increasingly uncomfortable with Sara's behavior. She tries to distance herself, but Sara's manipulations and threats keep her trapped. As Sara's actions escalate, Rebecca's fear grows, and she becomes increasingly isolated.
The tension intensifies, leading to a series of confrontations and dangerous situations. Rebecca starts to realize the true nature of Sara's obsession, and the threat it poses to her safety.
The climax of the film involves a confrontation between Rebecca and Sara, where Rebecca fights back against Sara's manipulation and attempts to escape her control.
The ending leaves the audience questioning whether Sara's obsession will truly end or if Rebecca will be able to fully break free. The film explores themes of obsession, manipulation, and the dangers of unhealthy relationships.