Liu Niang, a famous embroiderer in Rouge Lane, Bianjing, hanged herself to death in her embroidery building late at night. There was no sign of a fight at the scene, but there was a silver hairpin engraved with the word "plum". Shen Yanzhi leads a team to investigate the case. Because Su Qingci knows autopsy (taught by his father's old department), he accidentally helps him discover a trace of cinnabar in Liu Niang's fingernails, which attracts Shen Yan's attention.
