Dong Baek wakes up from the hospital to only find Mr. Noh missing. They try to find his traces and the connection between Mr. Noh and Chun Ki Soo. After a talk with his wife, Dr. Song, Dong Baek and Han Sun Mi find out that she covered up for a murder case 20 years ago. The deceased’s name was Moon Yong Dae. How will the incident 20 years ago help them find out who the Eraser is?