On the surface, the Dayin Dynasty was peaceful, but in fact, the vassal kings were separatist, eunuchs interfered with politics, Beidi suppressed the border, and the Qintian Prison was corrupt and neglected its duties. The protagonist Xiao Yan was an unjustly exiled Imperial College student, but was robbed and turned into a slave on the way. However, on the way to northern Xinjiang, he triggered the fragments of the ancient "Heaven's Secret Compass" in the ruins of the ancient observatory, and awakened the "Heaven's Secret Deduction" system - each deduction consumes "Mind Points", which can lock the cause and effect nodes of specific people, events, time, and places (for example, "At three o'clock in Shenshi, the deputy general You Xiaowei will draw his knife and stab the governor in the throat."). By deducing his innocence, solving crimes, relieving disasters, and retreating from the enemy, he quietly rebuilt the Tianji Prison, rectified the astrological calendar, calibrated the military map, and countered the witchcraft of the enemy country. He finally exposed the conspiracy of the imperial master to forge auspiciousness and collude with foreigners. On the eve of the new emperor's ascension to the throne, he shocked the court with a volume of "Tianji Proof and False Record". He was named "Supervisor" and was in the same position as the Third Duke. He was in charge of the power to deduce the national destiny.
