Im Dong-Hwan's (Park Jeong-Min) father, Im Young-Kyu (Kwon Hae-Hyo), is a master craftsman of seals even though he is visually impaired. One day, Im Dong-Hwan receives a phone call from police. He is informed that his mother Jung Young-Hee's remains were discovered. She went missing 40 years ago. Im Dong-Hwan, who never knew his mother's face, hears that there is a possibility that his mother may have been murdered. Im Dong-Hwan begins to trace Jung Young-Hee's death with PD Kim Su-Jin (Han Ji-Hyun), who was filming documentary about his father Im Young-Kyu. They interview people who worked with Jung Young-Hee at a Cheonggyecheon clothing factory about 40 years ago.