The plot’s development centers on Liu’s dark and rather gloomy but highly persuasive philosophy, with dazzling ideas and an unsettling, nonlinear, almost nonnarrative structure that demands patience but offers huge rewards. Luo has no idea why he was chosen, but, nonetheless, the Trisolarans seem determined to kill him. The chosen Wallfacers are soldier Frederick Tyler, diplomat Manuel Rey Diaz, neuroscientist Bill Hines, and-Luo Ji.

To combat this, the ETO creates Wallbreakers, dedicated to deducing and thwarting the plans of the Wallfacers. Four selected individuals will be accorded the power to command any resource in order to develop plans to defend Earth, while the details will remain hidden in the thoughts of each Wallfacer, where even the sophons can't reach. The Planetary Defense Council, meanwhile, in order to combat the powerful escapist movement (they want to build starships and flee so that at least some humans will survive), announces the Wallfacer Project.

This time, with the Trisolarans a few years into their voyage, physicist Ye Wenjie (whose reminiscences drove much of the action in the last book) visits astronomer-turned-sociologist Luo Ji, urging him to develop her ideas on cosmic sociology. Humanity’s lone advantage is that Trisolarans are incapable of lying or dissimulation and so cannot understand deceit or subterfuge. On Earth, the Earth-Trisolaris Organization formed to help the invaders, despite knowing the inevitable outcome. So, determined to capture Earth and exterminate humanity, the Trisolarans embarked on a 400-year-long interstellar voyage and also sent sophons (enormously sophisticated computers constructed inside the curled-up dimensions of fundamental particles) to spy on humanity and impose an unbreakable block on scientific advance.

In the previous book, the inhabitants of Trisolaris, a planet with three suns, discovered that their planet was doomed and that Earth offered a suitable refuge. Second part of an alien-contact trilogy ( The Three-Body Problem, 2014) from China’s most celebrated science-fiction author.

The dark forest problem