Unable to sleep after the warning that the universe would "flicker," Wang Miao calls Ding Yi at one in the morning to ask whether any Chinese facility observes the cosmic microwave background. Ding Yi says many scientists have recently "seen something" as well, urges Wang to visit Yang Dong's mother because she is an astrophysicist, and admits he cannot bring himself to face reminders of Yang. Afterward, Wang steadies himself by thinking through Frontiers of Science, Shen Yufei, and the strange V-suit game she had been playing, then decides to investigate the game himself at the nanotechnology center.

Logging into Three Body as "Hairen," Wang enters a desolate world and meets King Wen of Zhou and his follower, who are traveling during a "Chaotic Era." Wang quickly learns that this world's sun rises and sets unpredictably, sometimes vanishing for days and sometimes becoming lethally huge, so ordinary ways of measuring time or forecasting weather do not work. To survive, people endure savage swings between freezing and scorching heat, and they can dehydrate their bodies into leathery rolls and later revive by rehydration; when the follower can no longer continue, King Wen dehydrates him and makes Wang carry him onward.

As Wang and King Wen continue toward Zhao Ge, the game compresses long stretches of travel through alternating Chaotic and Stable Eras. King Wen explains that civilization can only grow during Stable Eras, while most of humanity must remain dehydrated and stored during chaotic periods, and that the purpose of the game is to discover a pattern behind the sun's motion so civilization can survive. When two "flying stars" appear, a Stable Era begins, reinforcing the idea that celestial mechanics govern the world's fate even if the pattern is not yet understood.

In Zhao Ge, Wang sees a kingdom trying to control the heavens through vast pendulums surrounding King Zhou's pyramid palace. Fu Xi argues that the sun is a god who can be lulled to sleep, but King Wen rejects this and presents a cosmological model based on yin-yang and the I Ching. Tested inside the pyramid, King Wen's calculations predict several coming Chaotic and Stable Eras with rough accuracy, including a long Stable Era, so King Zhou orders mass rehydration and civilization rapidly revives as stored bodies are restored from lakes and society begins anew.

The apparent success does not last. After eight orderly days, sunrise fails to come, the cold intensifies, and news arrives that three flying stars have appeared, a sign of catastrophic extreme cold. King Zhou orders dehydration again, King Wen submits himself to execution after his forecast fails, and the world freezes so completely that even carbon dioxide, oxygen, and nitrogen fall as snow. A final message announces that Civilization Number 137, which had reached the Warring States Period, has been destroyed after a forty-eight-year long night; before exiting, Wang notices the three stars revolving around one another in the sky.