Are Grace and Katherine related to each other? What would happen if the man Grace loves falls in love with another girl? What if Grace suddenly disappears without any trace? Will he continue to stand by his promise? Will he actually keep Grace in his heart? Or will he change Grace's place in his heart? What if one day... Grace comes back? Will the bond between the two continue at its usual level? Or will Grace untie the knot between them? What if the tied knot between them is untied by Grace herself? Can she continue living without him, on her own?