Set against the backdrop of China's Cultural Revolution, a secret military project sends signals into space to establish contact with aliens. An alien civilisation on the brink of destruction captures the signal and plans to invade Earth. Meanwhile, on Earth, different camps start forming, planning to either welcome the superior beings and help them or to fight against the invasion.
The Trisolarian fleet has left their home world and will arrive in four centuries' time. But the Sophons and their extradimensional emissaries are already here. This is the motivation for the Wallfacer Project, a last-ditch defence that grants four individuals almost absolute power to design secret strategies, hidden through deceit and misdirection. Luo Ji, an unambitious Chinese astronomer, is baffled by his new status. All he knows is that he's the one Wallfacer that Trisolaris wants dead.