In the twenty-eighth year of the Republic of China (1939), undercurrents surged in Shanghai after the fall. Su Jingming, the munitions supervisor, colluded with the Japanese side and used the underground fortifications of the mansion to carry out secret cooperation, and the forces of all parties were intertwined. Underground intelligence agent Shen Yan aliased Su Wanqing, the down-and-out daughter, and sneaked into the Su family's deep residence as the fifth concubine. While dealing with various temptations from the wives, concubines, and housekeepers in the house, she secretly contacted people in the house who wanted to resist. She circled among Japanese spies and informants from all sides, waiting for opportunities to find out the enemy's core conspiracy, and persisted in the latent mission in the battlefield where no gunpowder could be seen in the deep house.
