It's Really Kind of You(2015)

Original title: 참 친절하시네요

It is a late night and raining hard when suddenly a strange woman, wearing only lingerie, runs into a man, fishing at the lake, and asks him for help. Soon the man finds out that the woman is a mute then agrees to follow her. The woman brings the man to a hillock where her husband is tied up and bleeding, screaming to save his life in a large bag.