On her son's wedding anniversary, mahjong-obsessed Grace leaves her granddaughter Coco alone in the kitchen. When Coco video-calls her mother, Rachel, she senses danger, but the call cuts off. Grace ignores repeated calls, and Rachel‘s husband Luke dismisses her concerns while out with his first love. By the time Rachel arrives, Coco has died from gas poisoning, exposing a tragedy born of neglect and blind obedience.
