Li Xunhuan retires to Plum Garden with Sun Xiaohong. On a snowy night, he encounters Bai Tianyu, who entrusts his children to him, and takes Ye Kai and Bai Cheng as his disciples. As Ye Kai studies under him, he displays exceptional talent and an optimistic nature. The mysterious "Elder of Heavenly Secrets," Sun Baitou, appears from time to time to guide the two children, leaving them with a maxim: "The throwing knife is not a knife, the divine knife is not a knife. The human heart is like a knife: that is the ultimate blade." Word has it that Bai Tianyu, master of Divine Knife Hall, was ambushed at Plum Blossom Nunnery and surrounded by more than thirty experts. He fought to the death, but the killers remain unknown, and Divine Knife Hall was wiped out overnight. Li Xunhuan gazes at the stars that night, and remains silent for a long time...