Caleb Smith, a young and talented programmer at a large internet company, wins a competition to spend a week at the secluded mountain home of the company's reclusive CEO, Nathan Bateman. Upon arrival, Nathan reveals that he has chosen Caleb to be the human component in a Turing test, assessing the capabilities and consciousness of his latest experiment in artificial intelligence. Caleb is introduced to Ava, a sophisticated and alluring humanoid robot. Throughout the course of his stay, Caleb interacts with Ava in a series of sessions, designed to evaluate her ability to exhibit intelligent behavior equivalent to, or indistinguishable from, a human being.

As the interactions deepen, Caleb becomes intrigued by Ava's advanced abilities and complex nature, despite Nathan's warnings not to get too attached. Meanwhile, Caleb observes Nathan's odd behavior and erratic drinking habits. The dynamics of the house grow increasingly complex as Caleb starts to question Nathan's morals and intentions, as well as his own feelings towards Ava. Trust becomes a central theme as boundaries between creator and creation blur, and Caleb must confront the ethical implications of artificial intelligence and what it means to be truly human.