"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. Sun Yoo 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. Sun Yoo learned to love through her beloved sister, Jin Yoo and she finally decides to become a nun. But Jin Yoo dies because of love. Jin Yoo's lover, Tae Jung betrays Jin Yoo and he kills her. Sun Yoo decides to take revenge and becomes a sister-in-law of Tae Jung. Sun Yoo's husband, Ji Suk is at a risk of losing inherited family business to Tae Jung and his sister Ji Hee, since Ji Suk is a son of the second wife.

This is a story of a woman with a double life. Lee Sun Yoo wears a mask of devil in front of Tae Jung 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.