Imagine the universe as a forest, patrolled by numberless and nameless predators. In this forest, stealth is survival - any civilisation that reveals its location is prey. Earth has. Now the predators are coming. Crossing light years, the Trisolarians will reach Earth in four centuries' time. But the sophons, their extra-dimensional agents and saboteurs, are already here. Only the individual human mind remains immune to their influence.

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 from human and alien alike. Three of the Wallfacers are influential statesmen and scientists, but the fourth is a total unknown. 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.