"A woman who wanted to live a life of nun holds a dagger of revenge for her beloved sister!" There is a woman who thinks she shouldn't have been born. Seonyoo was born at a cost of her mother's death and her illnesses cost her family endless medical bills. She thought of herself low and she hated herself. Seonyoo learned to love through her beloved sister, Jinyoo and she finally decides to become a nun. But Jinyoo dies because of love. Jinyoo's lover, Taejeong betrays Jinyoo and he kills her. Seonyoo decides to take revenge and becomes a sister-in-law of Taejeong. Seonyoo's husband, Jiseok is at a risk of losing inherited family business to Taejeong and his sister Jihui, since Jiseok is a son of the second wife. This is a story of a woman with a double life. Lee Seonyoo wears a mask of devil in front of Taejeong but she takes off the mask in front of her family. She hides the dagger of revenge and the angel wings at the same time.