17 year-old A-Young has just given birth in a secluded spot by a railroad. Bleeding heavily, she tries to find refuge. Her boyfriend Hyung-gyu returns to the scene to help her only to find out she's left. He is soon chased by police officers who see the bloodstains and assume he is guilty of a possible crime.
Bori, an 11-year-old girl in a seaside village, is the only family member who can hear. As an elementary school student, Bori becomes more and more accustomed to talking with her friends while finding it hard to communicate with her family in sign language.
One day, 25 years ago, missing Chun-bae's letter is delivered to his cousin, Jjang-goo. The letter contains Chun-bae's lover, Bok-soon, and other people's letters. Jjang-goo finds Bok-soon to deliver the letter and meets class president Jang together. The three people recall their memories from 25 years ago, and eventually faced the person who sent the letter. Through that, the tangles begin to unravel.
