Saimdang, Bitui Ilgi follows the story of Seo Ji Yoon (Lee Young Ae), an art history lecturer who has dedicated her life to earning her Ph.D. and working under her mentor, department chairman Min Jung Hak (Choi Jong Hwan), in the hopes of becoming a full-time professor at her university.
When Jung Hak assigns Ji Yoon to write the thesis for the historical painting "An Gyeon's Mount Geumgang," she is thrilled as it could lead to her professorship. However, her world quickly falls apart. Her husband, Jung Min Seok (Lee Hae Young), becomes a fugitive due to his company's illegal activities, forcing Ji Yoon, her son, and her mother-in-law, Kim Jung Hee (Kim Hae Sook), out of their home.
Additionally, Ji Yoon's career suffers a blow when grad student Han Sang Hyun (Yang Se Jong) challenges the authenticity of the Mount Geumgang painting, leading to Ji Yoon's dismissal and ostracization from the art history community by Jung Hak.
At her lowest point, Ji Yoon discovers the secret diary of Shin Saimdang, a Korean artist, writer, and poet from the Joseon Dynasty. The diary reveals new insights into Saimdang's life, her relationship with painter Lee Gyeom (Song Seung Heon), and the Mount Geumgang painting.
With the support of Sang Hyun and her friend, Go Hye Jung (Park Jun Myun), an antiquities researcher, Ji Yoon sets out to reclaim her life and career. Will she be able to overcome the challenges and restore her reputation?