The plot is based on the literary trilogy "The Memory of the Past Earth" by science fiction writer Liu Cixin. The events take place in China during the Cultural Revolution. The story revolves around an astrophysicist named E Wenzhe, who is leading a top-secret project called "Red Coast." The protagonist writes a letter to aliens, inviting them to visit planet Earth... After some time, representatives of the special services encounter a mysterious and incredible phenomenon.