Seven Fiendish Detectives tells the story of a wealthy merchant family, the Liu clan, which is brutally wiped out overnight in Xiangzhou, a city in the Great Qian Dynasty. On the night of the blood moon, seven talented young people, Su Yichen, Lin Yushang, Xiao Yifeng, Ye Jinxuan, Mo Wuhen, Zhao Lingyue, and Chu Xingyuan, form a detective squad determined to uncover the truth behind this terrifying and bizarre case. Searching through the Liu family’s eerie old mansion, they discover all kinds of mysterious clues, including bloodstained fabric, a bloodied dagger, and a blurred account book. As their investigation deepens, they find that powerful figures in the city are involved, and that the case is riddled with conspiracies. In their pursuit of the truth, they repeatedly find themselves in danger and face life-or-death trials, but they never give up, closing in step by step on the astonishing truth hidden deep in the darkness.