Wang Miao attends another Three-Body meetup where Pan Han is denounced and killed for his killing of Shen Yufei by the commander of the Earth-Trisolaris Organization, Ye Wenjie.
Ye tells Wang that at Red Coast Base. she secretly discovered a way to use the sun to amplify the broadcast signal many times over, and 8 years later received a reply from Trisolaris, but it is a warning:
Do not answer!
Do not answer!!
Do not answer!!!
Ye, already disillusioned with the human race from the events of the Cultural Revolution, her father getting killed, and an escalating Cold War, quickly sends a reply inviting the sender to come to Earth and says she will help them conquer it.
She tells Wang that he needs to stop his nanomaterial research to ensure the Trisolarans can come to Earth to conquer it. Just then, Da Shi leads the police and army to take down the ETO. He quickly acts when a member says they have a nuclear bomb and shoots it, causing the conventional explosives to detonate, but prevents the nuclear explosion.
The police arrest the ETO members and interrogate Ye, where she reveals that she was the one that killed both her husband and Commissar Lei.
She had intended to only kill Lei after he discovered the message that the base had received from Trisolaris. She will cut his rope as he rappels down the mountainside to fix a ground wire that she had sabotaged. Her husband Yang shows up and also rappels down to help, and with no other opportunity, Ye cuts the rope, killing both of them.
In the following year she gives birth to Yang Dong and sees society move on from the events of the Cultural Revolution that killed her father, and ends with her “unshakable ideal”: “to bring superior civilization from elsewhere in the universe into the human world.”