Spoiler alert for those who haven't read "Death's End"
At the end of "Death's End," the final novel in Cixin Liu's "Remembrance of Earth's Past" trilogy, a few major events take place.
Firstly, the main protagonist, Cheng Xin, decides to surrender herself to the Trisolaran fleet in order to prevent them from attacking Earth again. She believes that, as a human, she is better equipped to communicate with the Trisolarans and negotiate a peaceful resolution to the conflict that has been ongoing throughout the series.
Meanwhile, a group of scientists on Earth led by Luo Ji are working on a plan to create a space-time tunnel that can transport human beings to a parallel universe unaffected by the Trisolarans. Despite the ethical concerns around abandoning their own universe, Luo Ji and his team believe that it is the only way to save humanity.
As Cheng Xin travels aboard the Trisolaran fleet, she begins to understand the Trisolarans in a way that humans have not been able to before. She learns about their past and their motivations, and realizes that their actions were not fueled by malice, but rather a desperate desire to save their own civilization.
Eventually, Cheng Xin and the Trisolaran leadership come to an agreement to end the war by allowing humanity to escape to the parallel universe. In a poignant ending, it is revealed that the characters we have followed throughout the trilogy have already left for this new universe, and the story closes with a brief discussion of what their new lives might be like in this different world.
Overall, "Death's End" delivers a satisfying conclusion to the trilogy, tying up loose ends and providing both closure and hope for the characters and the larger universe.