The Dark Forest

Luo Ji wakes up 185 years later on a technologically advanced Earth. He finds that humanity has built an advanced space fleet that is bigger and better than that of Trisolaris. Humanity’s view of the coming crisis has greatly improved, with their fleet over 1,000 ships larger than the Trisolar fleet. Only 300 Trisolar ships are expected to arrive for the invasion. Humans hope to discuss peace with the Trisolarans soon.

In this new world, Luo Ji is shocked to hear that few people now live on the surface and that most major cities are now underground, where food is engineered and microwaves are sent out to power all electric devices, eliminating the need for wires. His doctors know little of the Wallfacer program, other than that it is treated like a joke. They want him to take his assimilation slowly as so much has changed. When he is released, Luo Ji sees that underground Beijing is like a forest, with tree-like structures housing buildings like leaves holding the ceiling up. The Beijing he knew is still above ground, but this new city is 1,000 meters underground, with a sky projected onto the ceiling. He learns that this move is a preparation for the coming war.

Ben Jonathan, Luo Ji’s new Wallfacer handler, collects him for his final PDC hearing. Jonathan tells Luo Ji of the new world, explaining that the old power structures faded, and that Europe is now one country, Belarus and Russia combined, and that Canada split along linguistic lines. With no more global superpowers, the new independent Space Fleet became its own nation and is divided into three groups: American, European, and Asian. The PDC therefore transformed into the Solar Fleet Joint Conference (SFJC). At the hearing, the SFJC votes to end the Wallfacer Project, as they are confident enough in their starships to no longer need the program. Hines’ research hit a wall and Luo Ji’s cursed star is still there, leaving no hope for either plan to be successful. Luo Ji signs off to once again become a civilian while Hines and Keiko remain.

Keiko reveals that she is Hines’s Wallbreaker and that despite the “mental seal” now being illegal, Hines made four extra sealing machines and secretly distributed them to a group of “imprinted” soldiers. She explains that Hines always kept his identity as a defeatist and Escapist secret and that by slightly altering the code of the “mental seal,” he reprogrammed soldiers’ minds to have an undying faith in Escapism. The change in the code was so minor that even the sophons did not detect it at first, and the secret nature of the “imprinted” means that there is no way to know whether they survived. There may be a faction of the military secretly working against the SFJC’s goals.

Luo Ji must acclimate to his new life but is warned not to wake his family until he is completely adjusted. He is told that he no longer needs to worry about the ETO, as they were destroyed over a century ago and no longer pose a threat to his safety. Shi Qiang, woken and cured of his cancer, picks Luo Ji up and takes him into the city. Luo Ji discovers that a chip in his arm allows billboards and other technology to recognize and interact with him. As he and Shi Qiang walk around the city, a floating car crashes into the ground and Shi Qiang barely moves Luo Ji out of the way in time. They report an assassination attempt to the police but are laughed at. They decide to seek shelter in Shi Qiang’s apartment and on the way are almost hit by another car. As they approach the building, a manhole automatically opens and almost swallows Luo Ji. Both times, Shi Qiang only just saves him.

They arrive at Shi Qiang’s building and sit down to eat lunch in the lobby. Shi Qiang tells Luo Ji that his son also hibernated and is still alive. When a robot brings them their food, it quickly picks up a knife and moves to stab Luo Ji through the heart. Shi Qiang saves him, and they retreat to his apartment where two more attempts on his life are made. When Luo Ji orders sleeping pills, the machine gives him short-term hibernation medication that would kill him without the proper accompanying technology. Then he sits on a sofa that naturally conforms to the sitter’s body. The sofa, however, reforms itself to strangle Luo Ji. Police arrive and inform Shi Qiang and Luo Ji that the attempts on his life are due to a computer virus named Killer 5.2. It is a remnant of the ETO and lay dormant in the city’s system for all these years but was recently reactivated when Luo Ji woke. Its purpose is to kill him, and Luo Ji is told to take refuge on the surface, where there will not be enough advanced technology recognizing the chip in his arm to kill him.

Zhang Beihai wakes from hibernation and his unit of political reinforcements are tasked with trying to uncover any secret factions of the “imprinted” in the Space Fleet. The SFJC trust Zhang Beihai and his unit because they hibernated before the existence of the “mental seal” and therefore cannot be “imprinted.” Zhang Beihai is sent to Jupiter, where much of the Asian Fleet is based in preparation for the imminent arrival of the first Trisolar probe. His first target is Dongfang Yanxu, the captain of Natural Selection. At their first meeting, she gives him a pistol and says that if he finds her guilty, he can kill her with it.

Shi Qiang and Luo Ji arrive on the surface and meet Shi Qiang’s son, Shi Xiaoming. He takes them out of old Beijing into the countryside to his village where he farms with his wife and four-year-old child. He explains how, after Luo Ji hibernated, the economy plummeted, and environmental protections were lifted to provide resources for the army. This led to political turmoil and the desertification of much of the world. As the world eroded and famine spread, the world population dropped from 8.3 billion to 3.5 billion in half a century. This was called the Great Ravine. After this, people abandoned hope for the future and began living for the present. After this, attention was once again turned to the Trisolar conflict and technological advancements boomed.

Zhang Beihai learns to control Natural Selection from Dongfang Yanxu, who is considering resigning because of his review of her. He insists that she doesn’t. Elsewhere, on the Fitzroy-Ringier Station, scientists struggle to track the probe after its engine goes out and it becomes invisible. They decide to create a dust cloud in the outer part of the solar system by using a hydrogen bomb to disperse barrels of oil film collected from Neptune. This allows them to see where and when the probe enters the solar system, and a ship named Blue Shadow tracks it as it arrives, noticing that its engine has turned back on.

Back on Natural Selection, Zhang Beihai takes over as captain and immediately sets its course for another star, preparing the ship for departure. With limited fuel, the ship leaves the solar system, defecting from the SFJC with no ability to return. Zhang Beihai hails the Fleet Commander and reveals that this was always his plan. He has concluded that humanity will lose the Doomsday Battle and need some way to escape if their civilization is to persist. He faked his triumphalism for years to mask his plan and admits to killing the three scientists. Zhang Beihai explains his plans to Dongfang Yanxu, whose crew is now hostage on Natural Selection. He asserts that he has a duty to preserve human civilization. Four ships are sent by the SFJC to pursue Natural Selection but will not be able to catch it until it decelerates.

The Trisolar fleet passes through another dust cloud, and it is observed that one ship is not decelerating with the others. It will arrive 50 years ahead of schedule and humanity takes this as a sign that Trisolaris wants to negotiate peace. Celebrations break out in Luo Ji’s village and are only amplified with the news that the three fleets will all intercept the probe together. As the fleets depart from Jupiter to meet the probe, Shi Qiang and Luo Ji stay reserved, unsure of what is to come.

Ding Yi is also awake from hibernation and will be the one to intercept the probe. He is aboard Quantum and suggests to its captain that they prepare to go into deep space in case anything happens at the intercept. The probe is shaped like a droplet and Ding Yi does not trust it that it looks nothing like a probe. An unmanned ship approaches the probe and intercepts it, grabbing it and dragging it back to the waiting research vessel. When it does not immediately explode, the people of Earth celebrate this as a sign of peace. Opinions of Trisolaris turn to sympathy and the UN even prepares for peace negotiations. Ding Yi, now on the ship waiting for the probe, sees it arrive. He and his team examine it under the most advanced microscope and see that it is completely smooth, its subatomic particles held together by strong interaction, making it stronger than any material in the solar system. Ding Yi realizes too late that the probe is not a sign of peace but a show of force. Before he can warn the fleet, the probe activates, vaporizing his ship.

The fleet believes that the probe exploded, but it is travelling at an undetectable speed toward the fleet. The ships are aligned in a rectangular formation, making them easy targets. The probe strikes the ships, piercing their fusion engines and causing them to melt and explode. The probe does not appear on radar, making it impossible for the fleet to track it. Confusion freezes the fleet. The probe destroys 100 ships in two minutes. The probe can defy physics and alter its course with impossible speed, tracking down and piercing each ship. As the fleet understands that it is the probe attacking them, they fire at it, but it is indestructible and immovable. The technology gap between the two civilizations is too great and the probe destroys almost the entire fleet, with only Quantum and Bronze Age escaping into deep space. After this mass destruction, the probe heads for the sun, leaving survivors stranded in space in small lifecrafts.