The mighty Datang Empire has fallen into dusk, and the great He-he clan is in decline. Nobles and humans fight reluctantly, pursuing eternal life in vain. Wu Xin and Qing Luan worked together, solving a series of strange incidents, and cherished each other. Qing Luan loves him, but does not dare to confess, nor does he want to hold back. The mysterious letter broke daily life. In search of the truth, they were involved in violent and insidious events.