Arc 4The Secret of Mulberry Lake
Xu Qi'an joined the Heaven and Earth Society, helped Number Six evade capture, and gained favor with the Directorate of Astronomy while continuing to serve the Nightwatchers. During the imperial ancestral rites, cries from Mulberry Lake triggered the Nation-Guarding Divine Sword, leaving Xu Qi'an and the Society suspecting a hidden secret beneath the lake.
- Daoist Jinlian invited Xu Qi'an to join the Heaven and Earth Society and explained that its purpose was to kill his corrupted junior brother Zilian.
- Xu Qi'an joined the Society as Number Three, learned about its members and the troubles in Yunzhou, and reported what he knew to Wei Yuan.
- Xu Qi'an chose Heaven and Earth One-Saber Slash, then used the Qi-Observing Technique and accidentally hurt his eyes by looking at the Director.
- Number Six confessed to killing Earl Pingyuan over the earl’s trafficking ring, and Xu Qi'an helped him hide from the Nightwatchers and arcanists.
- Xu Qi'an resisted Jiang Lyuzhong’s attempt to transfer him, lectured Song Qing’s arcanists on alchemy, and received a dark-gold saber from the Supervisor.
- While guarding the ancestral rites at Mulberry Lake, Xu Qi'an heard cries for help that no one else could hear and shouted for them to stop, awakening the Nation-Guarding Divine Sword.
- Emperor Yuanjing continued the rites after the disturbance, while Xu Qi'an and the Heaven and Earth Society suspected that Mulberry Lake concealed a secret and Wei Yuan warned his subordinates not to investigate.