Middle-aged Liang Yuan is caught in an agonizing dilemma. His wife, Fang Qing, has a tumor and urgently needs treatment, while an old classmate tempts him with money, hoping he will bend the rules at work. Torn between his beloved's illness and his professional integrity, Liang Yuan is deeply tormented. A handwritten-letter assignment from his daughter stirs buried memories of his youth. Time rewinds to 1988, when fourteen-year-old Liang Yuan hid a letter to his future self in the hollow of a crooked-neck poplar tree. Fragments of childhood keep resurfacing. His mother, Chen Xiulan, teaches him with a wooden ruler that a person must have backbone and hold the line; as a boy, he stole money from home to rescue a stray cat and was severely punished by his mother.