During the Xining period of the Northern Song Dynasty, Gu Qingci, the young owner of the calligraphy and painting shop "Moxiangzhai" in Bianjing, lost his parents in a fire, but unexpectedly discovered half of the "blood-stained inkstone" left by his father - this inkstone can reveal the words or pictures hidden under the ink when exposed to old ink. In order to find out the cause of his parents' death, Gu Qingci was involved in the case as a "calligraphy and painting restorer". The first commission was extremely difficult: a "Fishing Alone in the Cold River" sent by the Yushitai, in which the fisherman's fishing rod contained a "secret letter fragment" covered in ink, and this secret letter was related to the mysterious drowning case of the Yushi three days ago.
After that, Gu Qingci borrowed the power of Duan Inkstone, and under the tracking and protection of the head catcher Lu Zheng, he solved strange cases one after another: "water patterned paper" that can change handwriting, "incomplete copybook" hiding poison formula, "ancient painting signature" with tampered year... Every time the inkstone is revealed, there will be clues to the power struggle between the "new party" and the "old party" in the DPRK and China, as well as a mysterious organization called "Moying Pavilion". And he gradually discovered that the death of his parents had long been a destined victim in this power game.
