Twin sisters, one mysterious countdown, and two wildly different fates. The elder sister, Fang Tianxing, carries a death countdown that ends at eighteen, and the entire family showers her with extreme love and indulgence. The younger sister, Fang Tianyi, is unfairly cast as the invisible one, enduring nine years of neglect, reproach, and cold violence. On the eve of her eighteenth birthday, Tianyi suddenly falls gravely ill, in agonizing pain, desperately begging her family to take her to a doctor—only to be dismissed as faking illness for attention and cruelly locked in a cold, dark storage room. The whole family is lost in the bittersweet warmth of spending what they believe is their elder daughter's last birthday, and no one gives a thought to the dying girl. Behind this tragedy of extreme favoritism hides a shocking secret that will overturn everything everyone believes.