Detective Yoo Ji Cheol receives a tip about a gambling parlor and is told to check the place out. He looks around the place but finds nothing suspicious and gets ready to leave. Suddenly, the owner of the place gives him a box full of beverages. He later on opens it to find a thick roll of cash.

While working, Seon Joo unintentionally attends the fan signing event for fighter Lee Min Woo. They seem to know each other from before, and he asks her how Ji Cheol is doing. Meanwhile, Ji Cheol gets interrogated for taking a bribe.

The bus Ji Cheol is in gets into an accident and turns over, and Ji Cheol realizes that the pills from the laboratory gives him superhuman strength. Meanwhile, his daughter tells him that Seon Joo has settled the dispute at school. Ji Cheol asks her if she received money from Min Woo.

After much consideration, Ji Cheol decides to fight at an illegal boxing match and contacts Kim Yong Dae of YD Promotion. However, during his first match, he sees that his opponent is in a physically different rank than him. After getting beaten up, he decides to take the blue pill once again.

Joo Gook Seong offers a big sum of money to Ji Cheol and asks him to play seven matches. In addition, he also tells him that he does not need to win every single time but just needs to attend them. However, Ji Cheol is very hesitant about this offer and cannot understand why Gook Seong would give him so much money.

Despite Seon Joo’s plea, Ji Cheol decides to accept Gook Seong’s offer and prepares seven pills for the matches. Young Seon finds out that her dad will be fighting again and gets frustrated. Meanwhile, Doctor Cha Seung Ho tries to convince Jeong Chan Joong that the drug is still too dangerous.

During a flashback of his match with Lee Min Woo who was a rookie back then, Ji Cheol gets a call and is offered three times his prize money if he loses the match. During the match, Ji Cheol suddenly stops throwing punches, and Min Woo ends up winning. However, everyone around him is suspecting him of purposely losing in order to receive money.

Sang A badmouths Ji Cheol in front of Young Seon, and they get into a fight. Ji Cheol is once again forced to face Sang A’s mother. When he tells Young Seon that he will not condone her fighting, she tells him that he is a fighter himself. Meanwhile, Seon Joo lies to Ji Cheol about going to Gangneung with Min Woo in order to avoid irritating him.

Young Seon decides to audition for “The Ultimate Dancer” alongside Sang A. After Sang A’s performance, the judges are in awe. When they ask Young Seon whether she will be performing ballet, Young Seon confidently says that what matters is whether she can dance well or not. Meanwhile, Min Woo tells Seon Joo that her novel will be published.

Young Seon passes the first round of the dance competition. Seon Joo finds out later on and congratulates her. However, when Young Seon asks Ji Cheol whether he has heard anything from her mom, Ji Cheol has no idea, and this upsets her.

The police retrieve the test subject Choi Yong Woo’s body but have a difficult time identifying him due to his marred face and missing hands. Furthermore, his wife decides to stand in front of the police station, begging them to find her husband. Meanwhile, a lab worker notices that two bottles of SF-3 is missing.

Suspecting her mom is having an affair and her parents, a troubled marriage, Young Seon purposely sets up a date night for her them without Seon Joo’s knowing. However, something pops up regarding the autobiography, and Seon Joo tells her that she will be late. Meanwhile, Ji Cheol waits for her at the restaurant.

During a flashback of the day Ji Cheol went to the laboratory to get tested and became acquaintances with Choi Yong Woo, Yong Woo is seen sneaking into the laboratory while the workers go on a lunch break. There, he secretly switches his name with Ji Cheol’s on the containers that have their blood samples in them. Meanwhile, Ji Cheol calls for a chauffeur, and Director Park appears.

Seon Joo wakes up late on the morning of Young Seon’s next show, and she ends up arriving late. To make matters worse, Young Seon trips while dancing, and the judges fail her, claiming that not making any mistakes is also a part of being a professional. Meanwhile, Min Woo decides to buy all 1,500 copies of Seon Joo’s book.

Only having a few more pills left, Ji Cheol tells Gook Seong that he will retire after fighting the remaining three matches in his contract. He then asks him to book his last fight with Lee Min Woo. Gook Seong tells him that there is no way he will be able to beat the current champion.

Ji Cheol hands Seon Joo the divorce documents and moves out of the house to the new house by himself. He tells her that he thought making money was all that mattered in order for him to support his family but that he was wrong. Meanwhile, Min Woo reminisces about the time when he confessed his feelings to Seon Joo. However, she rejected him, saying that she could not sacrifice their friendship.

Ji Cheol fights against Sang Goo and makes a dramatic turn of events. However, he gets caught taking something while getting a short rest. Lee Min Woo is impressed by Ji Cheol’s match, so he challenges him while Ji Cheol exits the stadium. Meanwhile, an intimidating man shows up at Jun Young’s house and turns the place upside down.

Ji Cheol learns about the real reason why Seon Joo decided to write Min Woo’s autobiography. He apologizes to her and the two clear their misunderstandings. Meanwhile, Seung Ho watches a video recording of Ji Cheol’s match where he takes the pills and realizes that Ji Cheol might be the key to his new drug development.

Dr. Cha Seung Ho from Shingoo Pharmaceutical comes to visit Ji Cheol at night. Dr. Cha explains that the drugs Ji Cheol has is still in development and asks how many times he has taken the drugs. Dr. Cha also talks about the side effects of the drugs. In the meantime, Min Woo visits Sang Goo to ask about the match with Ji Cheol.

Gook Seong believes that there must be something about Ji Cheol’s extraordinary strength. He visits Seon Joo to find out if she knows any secret to her husband’s conditions. Sang Goo also starts to suspect Ji Cheol of taking a drug. In the meantime, Chan Joong finds out that Ji Cheol is the only one who’s alive after taking the new drug and schemes against Ji Cheol.

Out of guilt, Ji Cheol decides to go against his opponent without taking the pills. However, the drug developers are keen to see Ji Cheol consume them so that he is in the right condition before any tests can be done on him. To make sure their plans don’t fall through, Director Park approaches Gook Seong to strike up a deal.

The match between Yoo Ji Cheol and Kang Sang Moon continues. Sang Moon corners Ji Cheol and keeps attacking Ji Cheol’s left shoulder and arm that Ji Cheol already got injured from the previous match. When everyone thinks the victory will go to Sang Moon, Ji Cheol drinks water that has the drug in it. Meanwhile, Ji Woo continues to investigate pharmaceutical companies and finally finds a photo from strips of shredded pieces of paper.

Ji Cheol runs away from home because of the guilt from seriously injuring Sang Moon. Yeong Seon gets worried about him and goes out to find him. While having a drink with Ji Woo, Ji Cheol notices that she has the same drugs he took during the match with Sang Moon. Meanwhile, Gook Seong calls in Ji Cheol to talk with him.

Gook Seong confesses that he’s the one who slipped in the drug in Ji Cheol’s water. Ji Woo tries to cover for Ji Cheol and tells Hyun Soo to stop the investigation on Ji Cheol. However, Hyun Soo continues to look into Ji Cheol in secret. In the meantime, Chairman Jeong of Shingoo Pharmaceutical tells Dr. Cha that he’ll involve Ji Woo, Dr. Cha’s daughter, in his scheme.

Ji Cheol hears that his declining performance was because of a type of amyotrophia. Gook Seong finds out that Ji Cheol is at his limit of using the drugs and prepares to set him up for a big rematch with Min Woo. Meanwhile, Hyun Soo manages to infiltrate the suspicious lab by disguising himself as a test subject.

Min Woo meets Ji Cheol and blames him and Gook Seong for ruining Sang Goo and Sang Moon’s lives. Ji Cheol gets angry after knowing the truth about what Gook Seong has done and runs off to see him. Meanwhile, Ji Woo receives a text from Hyun Soo and goes out to meet Woodpecker and find him.

Jin Sang Goo gets killed right in front of Ji Cheol. Dae Seong tries to hand over the evidence of Shingoo Pharmaceutical’s crimes to Ji Woo, but Doctor Cha stops him to save his daughter. Meanwhile, Jong Doo gets caught as the hit-and-run driver responsible for Sang Goo’s death, and Pil Doo visits him after hearing the news.

Jong Doo gets killed in the lockup. During Jong Doo’s funeral, Pil Doo decides to take his revenge and leaves the place. Chairman Jeong gives up on his attempt to kidnap Young Seon. Ji Cheol realizes the connection between Jong Doo and Sang Goo and visits Gook Seong. Meanwhile, something goes wrong while Yeong Seon practices before her live broadcast.

After hearing that Young Seon has a disease, Seon Joo is devastated and Ji Cheol is worried that her illness could be passed down from him. In the meantime, Ji Woo finds a video file filmed by Detective Lee, and the video file shows her father is involved in the illegal drug development. And she goes to see her father who is in hiding.

Young Seon’s condition is getting worse. Gook Seong visits the hospital and gives money to Seon Joo for consolation, but Seon Joo refuses. In the meantime, Ji Cheol agrees to become a test object as Chan Joong wants in the hope that the newly developed drug could help heal Young Seon. However, the test result is not promising.

Ji Cheol hands over a voice recording file of Gook Seong to the police and says he’ll pay for what he has done after having a match against Min Woo. Gook Seong keeps putting pressure Ji Cheol to take the drug before the match. However, Gook Seong ends up in an out-of-the-way place with a man who has planned to take revenge on him.

Ji Cheol and Min Woo fight each other with all their strength until the bell rings and even the commentators say Ji Cheol shows the best retirement match in history. Seon Joo and Young Seon watches the match on television in the hospital. However, Young Seon suddenly falls unconscious and Seon Joo gets panicked.