"Nine nine returns to one" can be translated as "All roads lead to Rome" or "Ultimately, everything boils down to one thing." The exact translation may vary depending on the context in which it is used, but it generally conveys the idea of returning to a single principle or outcome after many variations or complexities.

The narrative thread of the story mainly follows the life and emotional journey of Jia Fugui and Zheng Fengshi, a pair of half-brothers with different social statuses but sharing the same father, as they navigate through the 20th century. The story focuses on representative historical periods and events, vividly portraying their experiences in family bonds, friendship, love, conscience, hope, and resentment. It showcases the pursuit of truth in human relationships and adherence to the essence of humanity by the Chinese people, who possess an excellent cultural tradition and a strong awareness of change, against the backdrop of the tumultuous transformations that occurred in China during the 20th century.

Fugui and Fengshi were born amidst the chaos of the Eight-Nation Alliance's invasion of Beijing. They grew up with vastly different social standings, personalities, and values. Fugui, the son of a servant unaware of his true heritage, developed strong business acumen along with a character marked by honesty, humility, and patience. On the other hand, Fengshi, as the young master of the household, was passionate, unrestrained, upright, and kind, often lost in artistic dreams expressing his pursuit of a beautiful ideal.

Throughout their long and legendary lives, they and their families experienced warlord conflicts, revolution, resistance warfare, liberation, and the birth and growth of New China. Their interactions revolved around the core issues of interest and emotion, confronting choices between reality and ideals, new and old, beauty and ugliness, life and death, conscience and compromise. These encounters brought excitement, anticipation, pain, and conflict, painting a series of genuine and touching pictures of life.

As they both endured numerous hardships alongside the 20th century and approached the threshold of a new era, these two centenarians returned to the lakeside where they had first fallen in love. Reflecting on their lives, they realized that while all worldly matters are fleeting like clouds, the eternal truth lies in the sincerity and genuine pursuit of humanity, the adherence to its essence, and the ultimate choices made amidst joys and sorrows. Through it all, the story conveys a return to the fundamental and enduring aspects of human existence.