Chang'an Crossbow Case

In the third year of Zhenguan, a ghost carriage was hidden in Chang'an City. It changes its appearance every day and wanders irregularly among the 108 squares. The car carries a modified eight-niu crossbow that only two people can operate. Hu Shang, former Sui officials, and Li Jiancheng's remnants all looked like the real murderer. The Baiqisi Captain, Chang'an County Lieutenant, and Wannian County Lieutenant were ordered to solve the case within a time limit. When they were suspicious of each other, the first iron arrow pierced the chest of an official in the street - and the crossbow arrow was never aimed at an official. No one knows when, where or to whom the carriage will fire its next arrow...