Dong Baek and Han Su Mi captured their suspect, Jae Gyu, who is responsible for all the crimes that happened 20 years ago. They admitted him to the hospital after he almost died from the recent brawl.

In the recent episode of Memorist, Dong Baek continued to get information from Jae Gyu. He touched him while he was asleep, but he picked up nothing as his memories of the crimes he committed got erased. He confirmed that Jae Gyu is not The Eraser. Then, he convinced his team that they need to search leads from Jae Gyu's past that may point them to the mysterious person.

Jae Gyu opened his eyes and went back to sleep. Dong Baek touched his shoulder to check if his memories will wander. A memory came up, wherein Jae Gyu and his wife were together with their daughter, Sang Ah. It showed Jae Gyu's life after he was released from a mental hospital. He discovered that his wife tried to poison him and had an affair with another man.

Jae Gyu's tale as a murderer started when his wife cheated on him. He inherited a huge fortune from his family, but he suffered from depression and health issues because of them as well. Instead of taking care of what he needed to get better, she tried to poison him with the food she prepared for him. His wife got pregnant with another man and gave birth to a child he taught of his own blood. When he found out everything, he began to worship spirits and used his power to kill for injustice.

Su Mi interviewed Jae Gyu as soon as he woke up. She believed that Jae Gyu is the murderer with her own judgment. Jae Gyu insisted that The Eraser knows everything about him. The Eraser would take out his memories so he may forget every crime. Jae Gyu confessed that he was responsible for the crimes 20 years ago. But the current murders that happened, he doesn't know anything about it.

Su Mi insisted if he is also responsible for her father's death. Jae Gyu did not answer. Instead, he made a deal with her in exchange for information. He will expose what happened to Su Mi's father's death as soon as Song Ah and her family were sent abroad.

Shin Woong arrived in the holding room, hearing the interrogations Su Mi did to Jae Gyu. He sent everyone out and watched the recordings alone.

Meanwhile, Dong Baek and his team went to the apartment where Jae Gyu stayed after he left the mental institution. They searched for the man with marks on his right hand and suspected him to be The Eraser. Reaching the place, Dong Baek found the name of the person they were looking for. He found out that the man had mental illness left untreated. With the help of his old father, the man continued to live. However, he struggled with no medicines on hand. Dong Baek touched the man's head and found nothing relevant in his memory.

Jae Gyu continued to share his life with Su Mi at the hospital. He mentioned what urged him to come back to Seoul is to protect Song Ah. He preferred to stay abroad to live away with fear and stay away from The Eraser.

A few months ago, he received pictures from his daughter with a written note that says, "come back." He is worried about Song Ah and her family's welfare. The written words are from The Eraser, and he threatened Jae Gyu to return to spare Song Ah's family. They found Jae Gyu when the crimes a few months ago happened that link his name and about his past.

Jae Gyu mentioned his experience about the deaths in the past when he saw The Eraser and what he looks like. Dong Baek and Su Mi decided to check on Song Ah and her daughter. At Song Ah's house, they asked questions that relate to his father and her childhood. Dong Baek asked Song Ah to let him scan her memory. Song Ah agreed and asked if he can also track her husband.

Dong Baek started to check telepathy and found nothing that leads to his father, Jae Gyu. They asked to scan her daughter's memory. After Su Mi saw a drawing from the child that resembles red eyes and a black face, Dong Baek touched the child's head. He saw The Eraser's face below the underground tunnel that stands at Jae Gyu's backyard. Dong Baek confirmed to Su Mi that he saw The Eraser and touched his shoes to make contact with his memory as well.

Dong Baek and Su Mi hurriedly went to Jae Gyu's backyard and opened the tunnel. They got in and checked the area. It was dark but Su Mi saw a man wearing a black mask sitting in the corner. He approached her even if she told him to step back. Su Mi shot the man.