Tempted - Season 1 Episode 18 The Break Up
Overview: Si Hyun finds out that Tae Hee knew all along that Seok Woo was not his bio-logical father. She apologizes for waiting for him to tell her the truth instead of mentioning it to him first. However, he tells her that he wants to be alone. Meanwhile, Si Hyun has a talk with Young Won without knowing that she is Tae Hee's mother.