在古老的通谷县，高级妓女 sudden vanishes, while Lee Mansion's young master tragically perishes in the wilderness. However, his family swiftly and quietly buries him without a proper investigation. It isn't until Song Ci notices something amiss that he begins round-the-clock surveillance of Lee Mansion. To his shock, many inhabitants of the estate transform into 'grass people' under everyone's watchful eyes.
Just when Song Ci is on the brink of mystery, another grassman slaughter occurs in through valley county. Faced with a puzzling case, sabotage from colleagues and pressure from the court, Song Ci relies on his sharp intuition to uncover the massive conspiracy lurking behind these events: it turns out that the family of the late Tsing Queen, who was assassinated twenty years ago, has been plotting to assassinate the emperor.
This gripping tale of mystery and intrigue follows Song Ci as he pieces together the clues to solve the enigma of the 'grassman' murders and thwart the treacherous plans of the late queen's family. Will justice prevail, or will the darkness of deceit and betrayal consume the land?
