Humanity prepares for the inevitable Trisolaran surrender by debating exactly how generous they should be when they do reach the Solar system. They eventually come to an agreement they call the “Strong Survival Plan” that would grant rights for the Trisolarans to settle on Mars after the probe, now called the droplet due to it looking like a droplet of mercury, comes into visual range, and humanity considers it to be a peace offering gift.
Ding Yi, who has awoken from hibernation, leads a team to be the first humans to have physical contact with the droplet. They are just one ship in a combined fleet of over 2000, lined up in a rectangle formation that is sent to encounter the droplet as a show of both unity between humanity (but actually just so no fleet can claim they got there first) and a show of force to the Trisolarans.
When Ding Yi’s team gets to the point where they are able to physically examine it, they realize that no matter how powerful magnification they use, the object still seems perfectly smooth. At this point Ding Yi realizes that humanity has vastly underestimated Trisolaris’ technical capability since they are able to build large objects out of strong interaction forces, something humanity thought could only be done at the atomic level.
However, his realization comes too late for not just his team, but for nearly the entire combined space fleet. The droplet rapidly accelerates and unfathomably takes a precise route directly through the engines of the entire fleet, causing them to explode in succession “like a string of firecrackers.”
The only ships that aren’t destroyed in the attack are Quantum and Bronze Age, which only survive because prior to contact, Ding Yi convinced them to enter a deep-sea state, allowing them to escape at high speed when the battle started.
On the other side of the solar system, Zhang Beihai and Natural Selection continue to speed away, pursued by Blue Space, Enterprise, Deep Space, and Ultimate Law. Initially the goal was to capture Natural Selection, but after they learn about the droplet attack, they quickly realize they are now the only hope for humanity and form a new civilization called Starship Earth that faces an uncertain future of deep space travel.
Starship Earth tries to organize itself for survival and cooperation for the long journey ahead of them, but it is not too long before they realize that none of the ships have enough fuel and resources on their own to make it to any destination. Separately, they all make plans to capture the resources from the other ships while inflicting what they see as necessary casualties of the crews of those ships so they can continue. The leadership of the Natural Selection comes to this realization and goes to Zhang Beihai, now back in command, that he must fire infrasonic h-bombs to take out the crew but preserve the ship.
Zhang Beihai had already come to this realization and was prepared to give the order, but he hesitates at the last moment and is too late when Ultimate Law launches an attack first, killing Zhang Beihai, Dongfang Yanxu, and the rest of the crew. Blue Space was the only ship ready for the attack and ultimately was the only ship to survive the Battle of Darkness.
Meanwhile on the other side of the solar system, Quantum and Bronze Age have come to the same realization and ended up with Bronze Age killing the Quantum’s crew. Blue Space and Bronze Age accelerate away from the solar system to start their journey to distant stars.