In the third year of the Tianbao Era, operatives of Wolf Squad disguise themselves as merchants amidst the hustle and bustle in the western district of Chang’an city on the eve of the Lantern Festival. The operatives are waiting for the right moment to strike. Li Bi, director of Peacekeeper Corps, is under orders to apprehend the Wolf operatives that have infiltrated Chang’an. This covert operation is foiled, allowing the squad leader Cao Poyan to slip away. Li Bi sends Tan Qi to the jail to bring the convict Zhang Xiaojing, who is sentenced to death, to be tasked with continuing the investigation.
天宝三载,长安城内上元节西市开市人声鼎沸,一队狼卫趁机冒充商队混入西市,欲图不轨。靖安司司丞李必奉命追查狼卫,但秘密抓捕计划失败,狼卫首领曹破延逃脱。李必派檀棋前去大牢带犯人张小敬,委派张小敬继续追查,并向其讲明利害关系,答应事成之后恢复他的自由之身。张小敬对崔六郎的尸体进行解剖,从体内发现一张长安城的舆图,于是猜测狼卫今日有大的阴谋。