In 1960s London, a young woman named Carol is trapped in a small, dark apartment, where loneliness and fear begin to consume her. From the beginning, it is evident that there is something unsettling about her behavior: her aversion to human contact and her inability to establish normal relationships plunge her into a state of constant anguish. Carol is a manicurist working in a salon, but each day she feels increasingly isolated as her mind begins to deteriorate.
The situation worsens when her sister, who has been caring for her, decides to move in with her partner. Suddenly, Carol finds herself alone in her claustrophobic space, where the sounds of the streets and the shadows of her own world seem to come to life. As time goes on, disturbing visions and paranoia take over her mind; the men who once seemed indifferent to her now terrify her.
The psychological tension spirals down into madness, making the viewer feel Carol's pressure and desperation. Her struggle to maintain control becomes increasingly desperate as reality and fantasy intertwine in a terrifying way. In a plot that explores the fragility of the human mind, the conclusion culminates in a chilling climax, where what has remained hidden finally emerges, leaving an indelible mark on the psyche of those who dare to observe.