Following aerospace engineer Cheng Xin across centuries of hibernation as humanity's relationship with the Trisolarans shifts from terror to détente to catastrophe, the final volume of the trilogy takes its scope to literally cosmic dimensions, exploring the true nature of the universe's reduction from ten dimensions to three, and the last survivors of a dead Earth. Vast, melancholy, and astonishing in its ambition, it is the most emotionally devastating installment of the trilogy.