Ye Wenjie tells her story of her time at Red Coast Base. She serves under a cover story working in the transmission and monitoring departments. Only after she gains the trust of Commissar Lei does she get told the true purpose of the base, the Search for Extraterrestrial Intelligence (SETI.) However, Ye laments that no contact was ever made or received, and that the base eventually ran out of funds and closed. Also during her time at the base she married Yang Weining, and together they had a daughter, Yang Dong. However an accident at the base killed both Yang and Lei.
In Three Body, Wang tries to convince European scholars such as Galileo and Aristotle that the world actually has 3 suns only to be not believed before seeing a tri-solar day destroy civilization once more. Afterwards he is called to the office of Da Shi, where he meets Wei Cheng, Shen Yufei’s husband.
Wei, a naturally gifted, but very lazy, mathematician, tells the story of how he met Shen at a Buddist temple and leaves to join her when he is offered unlimited resources to try to solve a problem that has vexed mathematicians, the three-body problem.
Wei reports that recently he has been threatened both by phone to stop his research and by Shen herself to continue his research. When he accompanies Da Shi and Wang Miao to his house, he finds that Shen has been murdered. Pan Han is the primary suspect since Wei had heard them arguing about the arrival of a “Lord” earlier, but he is nowhere to be found. Wei then asks Wang to take his solution to the three-body problem and publish it
Wang again enters Three Body and sees another failed experiment this time that included millions of soldiers forming a human computer to run calculations to predict the Stable and Chaotic eras. After the civilization is once again destroyed, Wang is invited to a meet-up of other players.
At the meet-up, Wang finds that the organizer is Pan Han, who tells the assembled players that the world of Three Body is actually a real place called Trisolaris. The point of the game and the meet-up is to find people sympathetic to the cause of the Trisolarans coming to Earth to conquer the human race. Wang plays along to find out more.
Wang sees that even more catastrophic events have happened to Trisolaris in the Three Body game. The planet has split in two and is theorized that they will eventually fall into the sun. The only way for their civilization to live on is for them to leave. The Trisolarans develop interstellar ships that can travel 1/10th the speed of light. Wang is able to watch the fleet take off for the nearest star 4 light years away.