On her daughter Lizzy’s birthday, Eleanor receives a video call from Lizzy, revealing she’s been locked alone in a car under the scorching sun, on the verge of death. Meanwhile, her husband Mason is at an amusement park with Selene, the widow of his late best friend, and her daughter Dolly. As Eleanor desperately searches for her daughter, she faces deception and suppression from those around her. Emotionally shattered, Eleanor gets help from Benjamin, a surgeon and her former junior schoolmate. They find Lizzy trapped in Selene’s car, suffering from heatstroke and unconscious—but it’s too late. Lizzy tragically dies. After reading Lizzy’s diary, Eleanor resolves to divorce Mason, ending a marriage filled with deceit and indifference.