After being kidnapped and forced to work as a servant in the rear palace, former apothecary Maomao inadvertently draws the attention of the higher ranks when she investigates what's causing the emperor's infant heirs to fall mysteriously ill.

Tasked with investigating a ghostly woman dancing nightly on the palace walls, Maomao finds a sleepwalking Concubine Fuyou. But with no medicinal cure for sleepwalking, she's forced to dig deeper to find the real reason behind Fuyou's affliction.