A doctor raises her three adopted daughter by giving them all the love she can. However, what she wants more than anything is to be allowed to see her real son who is being raised by the boy's father.
The royal family has no male heirs to carry on the bloodline so, when the queen gives birth to yet another princess, the head of the court maids exchanges the infant princess with the newborn son of a servant.
Jae-seon falls in love with Ki-seok unaware that he is her sister's ex.