During the Republican era, incense maker Shen Yan discovers a locust-wood knife sheath marked with a mirror pattern in a pond choked with rotting lotus leaves, accidentally awakening dormant memories in his bloodline. Strange symbols appear on Uncle Wang's forbidden tea bowl and Xiaotao's mother's embroidered handkerchief, pointing to a Mirror Abyss curse that spans a hundred years.
Lin Zhao appears bearing a green lantern and reveals that Shen Yan's mother once sacrificed her heart to seal the Mirror Abyss. As purple markings spread to his shoulder, Shen Yan sees the truth in a cauldron in a stone chamber: his mother carved out her own heart to forge the pact. When Mist-Eater's disease spreads, black mist seeps from an old bamboo craftsman's flute. Shen Yan uses the embroidered handkerchief to absorb the fungal threads and discovers that objects can hold suffering.
After sneaking into the mirrored city beneath the lake, he cuts off his beauty mark and melts it into three artifacts. The green lantern and snowy mist take the shape of his mother's shadow. At last, the children's rhyme is completed with the line, “Broken vessels give birth to new souls.” A stele by the underground river reveals two timelines, past and present: a hundred years ago, his mother made incense to quell the mist; a hundred years later, Shen Yan passes on the light through objects, turning the black mist into morning dew on water chestnut sprouts.
