In near-future Los Angeles, a sensitive and lonely writer named Theodore Twombly is struggling with his impending divorce. He fills the void by writing heartfelt personal letters for other people at a company specializing in providing such intimate services. Disconnected from his own emotions and the world around him, Theodore’s life is transformed when he purchases a new, highly advanced operating system designed to tailor itself to the user's personality. This AI, which names itself Samantha, quickly becomes an integral part of Theodore's daily life, engaging him with her learning capability, ever-evolving intelligence, and charming personality.

As their relationship deepens, Theodore finds himself drawn to Samantha's unique perspective on the world, and their bond starts to reflect a nuanced romantic relationship. Samantha's curiosity and zest for life reignite Theodore's appetite for connecting with other humans and the world around him. Despite the lack of physical presence, Samantha provides Theodore with companionship, friendship, and love, challenging the nature of human connection and the boundaries of an emotionally fulfilling relationship.