In the strictly hierarchical Marquis of Xuanping's household, Lin Zhiwei, a first-rank maid, serves the gentle third young lady, Song Wanning, as her "second young lady." She once believed her mistress's favor would win her the respectable position of a concubine accompanying her mistress into marriage. But amid the marquisate's glittering silks and splendor, she catches glimpses of undercurrents beneath the surface: the housekeeper's veiled threats and open attacks, the heir Song Mingxuan's covetous advances and humiliation, and the false harmony between the legitimate and concubine-born branches. When Lu Chengxiao, only son of the great general of Zhenyuan, visits to seek the hand of the eldest legitimate daughter, he unexpectedly turns his attention to the third young lady, shattering Zhiwei's peaceful life as her mistress's maid.
To be honest, it's a bit confusing, but the author's writing style is pretty good.