Yun Xi, master of Yun Xi Valley, is peerless in both medicine and poison and unmatched in martial arts. He shares a tangled love-hate history with his sworn enemy and has a son, Yun Sheng. In his thirty-seventh year, he meets the five-year-old orphan Qin Nanxi at Cold Light Temple, takes her as his personal disciple, and brings her back to the valley to raise alongside his ten-year-old son, Yun Sheng.
Since childhood, Zhouzhou has called Yun Sheng “big brother.” They train in martial arts and learn to identify medicinal herbs together, spending every day at each other's side and understanding one another without words. As they grow up, they prove evenly matched in martial arts, each with their own strengths: Yun Sheng's skill with poisons is unrivaled in the valley, while Nanxi practices medicine with a compassionate heart, healing the world.
On the eve of his death at the age of fifty, Yun Xi and his eldest son, Yun Sheng, make a joint decision. Breaking with tradition, he will not pass the position of Valley Master of Yun Xi Valley to his own son, but instead bestows it upon Qin Nanxi, who is only eighteen years old.
