Sun Mi finds out that Dong Baek was at the scene of the mass murder in Shimbae City 20 years ago. However, she decides to continue with the joint investigation after a brief interrogation at Jin Jae Gyu’s house. Eventually, Sun Mi and Dong Baek realize what the Eraser’s ultimate goal is as they finally face those behind the grand scheme.

Right after telepathic, superstar detective Dong Beck gets put on disciplinary probation for assault, an out-of-the-ordinary kidnapping and serial killing occur. Elite profiler Han Sun Mi, the nation's youngest senior superintendent, first takes on the case. With his hands tied, Dong Beck also secretly joins in on the chase. The two genius crime solvers independently pursue a serial killer with a hammer.

With the execution time only getting closer and hindered by the dominant authoritative power that only wants to cover up the case, both Dong Baek and Sun Mi's separate chase to save the lives of the kidnapping victims slams into a brick wall. However, Dong Baek continues his pursuit with only the ambiguous clue of the Claw Hammer serial killer, a mysterious image of a red pig seen in one of his memory scans.

Sun Mi thinks that the person who has a superpower could be the culprit, so she adds Dong Baek to a suspect list. Dong Baek starts investigating the person who sent a drawing to Ki Dan thinking that the person is the culprit. Meanwhile, Dong Baek goes to Sungjung Sanatorium to meet Young Moon, and he reads Young Moon’s memory.

Jin Jae Gyu actually was the Executioner who killed Sun Mi’s father 20 years ago, but he wasn’t the Eraser who recently surfaced as a telepathic murderer. In fact, he had no choice but to become the Eraser’s puppet in order to protect his family. What was left of his memory is Dong Baek and Sun Mi's only lead to track down the Eraser. And when they finally do find a relevant case, they also realize that the Eraser recently physically contacted Dong Baek.

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?

Dong Baek meets face to face with the Eraser to only find out it was his older sister, a long gone memory he erased himself after a traumatic family event. After finding his old memories, he laments to the fact how his sister turned into a killing monster. However, thankfully, he collects ample evidence to prove Hwang Pil Seon and Bang Joon Seok’s crimes.

Dong Baek and Sun Mi finally come face-to-face with the real Claw Hammer serial killer. Now, it's a fierce race against time—Dong Baek and Sun Mi, who are working together to secure murder evidence, against those who want to destroy it. However, within their battle, they face yet again another catastrophic event.

Sun Mi thinks that the person who has a superpower could be the culprit, so she adds Dong Baek to a suspect list. Dong Baek starts investigating the person who sent a drawing to Ki Dan thinking that the person is the culprit. Meanwhile, Dong Baek goes to Sungjung Sanatorium to meet Young Moon, and he reads Young Moon’s memory.

Assemblyman Bang’s wife, Eun Soo Kyung is captive and photos of her being tortured is sent by the Eraser. The whole media is spreading the hideous acts of the villain while putting Dong Baek as an accomplice. Dong Baek, and Superintendent Han’s crew struggle to find out who Eraser is. On the day of Assemblyman Bang’s urgent press conference, Dong Baek interrupts by scanning Mr. Bang’s memory.

After finally discover the image of the red pig, Dong Baek races to a farm to save Ye Rim, the kidnapped girl on the brink of execution. Meanwhile, Sun Mi all by herself heads to where her instincts guide her and enters the serial killer's hideout, risking her life. However, they come across something they never expected.

When all the clues point to Jin Jae Gyu, proving that he could be the Executioner, Dong Baek and Sun Mi approach him for a memory scan. However, he refuses it and chooses to go through a house search. Although plenty of evidence related to murder cases is found, it was not solid enough to keep him in custody. Instead, Jin Jae Gyu provokes Dong Baek and Sun Mi with a prophecy of another murder.

Dong Baek is so close to catching Jin Jae Gyu, the culprit of all the murders. As Dong and Han track down Jin Jae Gyu, the two still can’t seem to find the ultimate reasoning behind Jin Jae Gyu’s massive acts of murder. They meet Sang Ha and her son Hyeon Su who also seem to be related with Jin Jae Gyu. Is Jin Jae Gyu really the Executioner?

Dong Baek and Sun Mi once again set out on a joint investigation to dig deeper into the concealed mass slaughter case from 20 years ago. While searching for the traces of the murderer’s identity, they finally secure an important clue that the murderer has a big scar on his right arm. However, there was one thing that they overlooked. The fact that there is someone around them with a similar scar.

While Captain Koo struggles to pull himself back from the brink of death, Dong Baek leaves a video with his testimony, knowing that it could put his life at risk. Before heading off to chase the Eraser, Dong Baek asks Ji Eun to release the video to the public at all costs. At last, Dong Baek and Sun Mi come face to face with the Eraser and shocking truth.

The Eraser leaves nothing in Yoo In Tae’s mind. Witnessing the critical condition the Eraser left Yoo In Tae in motivates Dong Baek and Superintendent Han to use a different strategy. They decide to come up with a step by step plan to lure and capture the Eraser. Will it work this time?