Yue-er is about to recover Tianming when the spell begins to counterattack and poison herself. Gongshu Chou claims he has found out the fatal weak point of the Machinery City. Duanmu Rong arrives in time and saves Yue-er and Tianming. Wei Zhuang gives a tiny bottle of poison to his spy, who disguises himself as Duanmu Rong and deceives Gao Jianli who guards the Centre Pool. Master Xun sees Ge Nie doing something to the pool and is wounded. In fact, that man is the Wei Zhuang's assassin, Heiqilin(Black Kilin). He has disuised himself as the Mohist who run for help and entered the City. He puts the poison into the water which flows everywhere and gives power to the whole city. Gao Jianli tries to kill Ge Nie but Duanmu Rong stops him.
卫庄得到了机关城的设计图，公输仇断言可凭此进入机关城内，并找到瓦解机关城的弱点。高月想要压制天明身上的咒印，却差点被反噬昏迷了过去，端木和徐夫子及时赶来救助天明，徐夫子将他们赶出炼剑池，对少羽的疑问避而不答。徐夫子在巡视机关城重地中央水池时遭到暗算，小高断言是盖聂所为，两人发生冲突之际，端木蓉挺身而出。
