The fourth season of the animated series "The Book of Hundred Demons" tells the story of Tao Tian, the little monk Mo Ya, the little fox demon Gun Gun and Tao Du's old neighbor Liu Gongzi, who continue to travel around the world in search of the missing Book of Hundred Demons. On the way, they encounter six monsters, An Dao, Bai Zhi, Feng Guo, Shu Hu, Feng Sheng and Dan Yu, and they treat various difficult and complicated diseases for the monsters.