Awful plot twists

Really i have never been so disappointed with a tv show, ever. This k drama starts with a serious and powerful argument, promising greatness becauae of very good casting and again, arguments. But NO... at episode 12 or so, everything started to crumble in a very confusing way. All the arguments at the beginning seemed to fade away for no reason, main characters started to be unrecognizable and actually i dont even know what was the final objective. Just awful. If you watch it prepare for very lazy writing...