Without Anyone Knowing

Chae Yeonah attends a blind date in place of her younger sister, Chae Sia, who is undergoing treatment for a serious illness. The man she is meant to meet is Seo Jeongju, heir to the Seonghwa Group and the object of Sia’s longtime platonic love.

Jeongju quickly falls for Yeonah and rushes toward marriage. Still pretending to be her sister, Yeonah goes so far as to marry him. However, when Sia recovers and moves into Jeongju’s home, he begins to sense that something is strangely amiss in his newlywed life.

Everything changes when their father, Chae Chungsu, mistakes Yeonah for Sia and accidentally reveals the truth. Yeonah discovers that she was deliberately abandoned at an orphanage and that her father and sister have only kept her close to use her as a potential kidney donor for Sia.

When Yeonah tries to make the truth public, Chungsu, who is preparing to run for president, decides to eliminate her. However, due to a mistake by the hitman, Sia is involved in the accident instead of Yeonah and falls into a coma.

Taking advantage of the situation, Yeonah assumes her sister Chae Sia’s identity and begins living her life while preparing to take revenge on the family that used and discarded her.