When Shen Zhi, an astronomer in the Northern Song Dynasty, was proofreading the Chongtian Calendar, he accidentally discovered a set of regular calculation errors. This is not an oversight, but a code that hides the military deployment of the Song Dynasty's border defenses. What is even more shocking is that the key to deciphering this set of codes is actually in the hands of an undercover Liao Dynasty lurking in the court. The stars have become a battlefield, and the calendar has become a blade. Shen Zhi must uncover the hidden double agent before the deadline to issue the calendar to the world, and destroy the "heavenly book" that can make the enemy march through mountains and rivers.
