After returning home, Wang Miao follows Shi Qiang's advice to drink, but he still cannot sleep. He buys a V-suit, ignores his unease by planning to return to work the next day, and then logs back into Three Body. He finds that vast stretches of time have passed in the game world: King Zhou's pyramid has eroded and been rebuilt into an observatory, showing that multiple civilizations have risen and fallen since his last visit.

At the observatory Wang meets Mozi, who explains that several more civilizations have appeared since Civilization 137, none of them able to master the unpredictable motion of the sun. Mozi shows Wang the frozen remains of Confucius, whose orderly cosmology failed when the sun abruptly went out, leaving behind a "flying star." Mozi presents his own mechanistic theory that the universe is a double-shelled sphere moved by forces from a surrounding sea of fire, and he proudly demonstrates a giant machine built to model the heavens and predict future Stable Eras.

Although Wang admires the machine, he doubts its explanation because it cannot account for the sudden disappearance of the sun or the significance of the flying stars. Using Mozi's telescope, Wang closely studies the sun and notices structural details unlike an ordinary sun, which convinces him that the game contains hidden astronomical information rather than decorative fantasy. He then spends more than ten in-game days observing the sun and flying stars, using accelerated time to detect patterns that Mozi overlooks.

On the seventeenth day of the predicted four-year Stable Era, sunrise is late, and Wang warns Mozi that the era may already be ending. Mozi trusts his model and reassures the crowd, but the delayed dawn becomes a disaster: an enormous sun rises, fills the sky, and burns the world. Animals, people, lakes, and finally Mozi himself are consumed by the heat, and Civilization 141 is destroyed in fire. The catastrophe proves that Mozi's system has failed and leaves Wang feeling that the game is concealing a deeper reality.

The next day Wang returns to the Nanotechnology Research Center and uses work to steady himself, but the night sky quickly revives his dread. Seeking emotional stability, he visits Ye Wenjie, whose calm presence comforts him. Ye recalls Red Coast Base, says that public accounts of it are inaccurate, and offers to tell Wang what really happened there, opening a path toward answers about the larger mystery.