The Three-Body Problem is a 2006 science fiction novel by Chinese author Cixin Liu. The novel is the first in the Remembrance of Earth’s Past trilogy, in which humanity deals with the arrival of an alien species from another galaxy. The Three-Body Problem won numerous awards and has been adapted for television, including an upcoming English language series scheduled for release in 2024.

This guide refers to the 2016 Head of Zeus edition, translated by Ken Liu.

Content Warning: The novel contains depictions of torture and death, including death by suicide.

Plot Summary

During the Cultural Revolution in China, Ye Wenjie watches a group of radical students beat her father to death for refusing to update his scientific theories in accordance with their ideology. After graduating, Ye is sent to a labor camp in Mongolia, where she witnesses a vast deforestation project. She meets a reporter named Bai Mulin who gives her a censored book to read. When she helps Mulin write a protest letter to the government, he frames her for radical behavior. Rather than be punished, she’s given the opportunity to work on a secret military base named Red Coast.

The Red Coast Base is at Radar Peak, a large mountain with a giant radio antenna at the top. Ye meets a scientist named Yang Weining and a political officer named Lei Zhichang. Ye isn’t afraid to give up her life and her freedom to work on the base, though she struggles to learn about the real purpose of the base and the giant antenna.

In the present day, a scientist named Wan Miao works on experimental nanomaterial technology. He has been invited to join a mysterious group named the Frontiers of Science. Although their academic debates interest Wang, he’s more focused on applied sciences than abstract theories. He’s then invited to the Battle Command Center, where he’s surprised to find representatives of many world militaries working together toward an unspecified cause. He doesn’t know what their enemy is, but people from the Chinese military, the police, and the North Atlantic Treaty Organization (NATO) countries are preparing for war. Their cause, he learns, relates to the recent wave of deaths by suicide in the academic community. Under pressure from a bullish police officer named Shi Chang, Wang agrees to go undercover in the Frontiers of Science.

In the following days, Wang is terrified to find a mysterious countdown, first in his photographs and then in front of his eyes. He visits Shen Yufei, who first invited him to the Frontiers of Science, and meets her husband, a lackadaisical man named Wei Cheng. He sees Shen playing a video game named Three Body. According to Shen, the countdown will vanish only when he stops his research. At home, Wang begins playing Three Body. The video game inserts players into a mysterious world where iterative civilizations try to deal with the cycle of Stable and Chaotic Eras, which repeatedly wipe out all life based on a seemingly unpredictable cycle of three suns that pass overhead. Progression in the game is dictated by the players’ ability to comprehend this three-body problem.

Wang visits Ye Wenjie, now retired, and she talks to him about cosmic radiation and the Red Coast Base. There, she says, she worked on the search for extraterrestrial life, but the base’s mission ended in failure. Returning to the game, Wang solves the three-body problem and is invited to join a players’ meet-up. During this time, Shi and Wang meet Wei, who explains that he’s working on his own theory about the three-body problem. A notorious environmentalist named Pan Han has been harassing him, telling him to stop. Pan murders Shen. When Wang attends the meeting, Pan is the host. He reveals that the contents of the game are real. The game world is based on the plight of an alien race four light-years away named the Trisolarans. The players debate whether the arrival of the Trisolarans on Earth would be good for humanity, whom they argue can no longer be trusted to look after Earth.

Wang learns that Ye Wenjie is the leader of the Earth-Trisolaris Organization (ETO). Many years ago, she contacted the Trisolarans and told them to come to Earth. The ETO is now divided along lines of those who want the aliens to annihilate humanity and those who want to work with the Trisolarans. The Trisolarans are already traveling to Earth and will arrive in roughly 450 years. The aliens developed technology—which they sent to Earth—that will limit humanity’s scientific research, preventing humans from innovating in time to stop the Trisolarans. The current hoard of communications with the Trisolarans is kept on a secret boat owned by a billionaire named Mike Evans. The Battle Command Center launches a military mission to regain this data, using Wang’s nanomaterials.

As Wang becomes increasingly hopeless, Shi reminds him that humans have tried to exterminate bugs for centuries, but bugs have endured despite the technological imbalance. Ye returns to the now-closed Red Coast Base and throws herself off a mountain.