The episode commences with a flashback, where Woo-gyeom wakes up in his cozy home, surrounded by his proud mother, Hye-ju. She dotes on him as they prepare for the contest that will announce the chosen thesis. His teacher suggests that Woo-gyeom has been selected, and Professor Han wants to meet him. However, on the way back, tragedy strikes: Woo-gyeom is hit by a car.
In the present, Woo-gyeom awakens in his old home, with blood loss that only a match of the same blood type (Rh null) can rectify. Thankfully, Han-jun's daughter, Min-seo, has been successfully cured.
Woo-gyeom and Han-jun embark on a heart-to-heart conversation, cementing their friendship. They reflect on their past dynamics and jest that things might have been smoother if they had trusted each other from the start. Woo-gyeom thanks Han-jun for being a good father and reveals that Jeong-su is tracking him. He leads Han-jun to the bridge where his mother's death took place, where he confides in him about his elaborate plan that all began with Jeong-su.
Flashbacks show Woo-gyeom being rushed to Cheum Hospital after the accident. Jeong-su, like his father, is obsessed with finding a cure for the incurable, which is why he approves Han’s proposal to experiment on Woo-gyeom. Two weeks later, Detective Gong tries to convince Hye-ju to abandon her search for her son. When she persists, Cheum Hospital claims that Woo-gyeom has been killed. But their story doesn’t hold up, and she begins to dig into Cheum Hospital’s illegal experiments. When she gets too close, Jeong-su has Director Ahn kill her and dispose of her body by the bridge.
Impatient with the slow progress, Jeong-su brings in a new research team and keeps a close eye on Han. Frustrated by the delays, Han escapes with Woo-gyeom when he wakes up. It's implied that Dr. Song Min-su betrayed Cheum by joining Han, prompting Jeong-su to have Shin kill Dr. Song.
Woo-gyeom gets pulled into his mother’s investigation when he discovers her research on Cheum Hospital. She had also compiled a list of anti-corrupt players to help her, such as Prosecutor Cha, Han-jun, and Reporter Jo. This is why Woo-gyeom approaches them – his original motive was to take down Chae Jeong-su after perfecting his cure.
Jeong-su, in a dramatic turn of events, shows up at the bridge and attacks both Han-jun and Woo-gyeom for their selfishness and irresponsibility. He insults their families, and Woo-gyeom, enraged, tries to punch him. Shin Ho-chang steps in and hurts Woo-gyeom. Jeong-su, prioritizing the cure above all else, beats Woo-gyeom for harming an asset. He begs and pleads with Woo-gyeom, hoping to start anew.
Woo-gyeom, in a moment of contemplation, calls Jeong-su out for his selfishness and brutality despite being a victim. However, Jeong-su reveals that he willingly offered to be his father's test subject and sees it as an honor to have Cheum find the cure. This revelation further enrages Woo-gyeom, who is consumed by anger at Jeong-su's disregard for humanity.
Just then, Prosecutor Cha arrives with the police. Worried that Jeong-su will escape, Woo-gyeom tries to kill him. Both Han-jun and Cha try to reason with him, with the prosecutor even revealing that she has enough evidence to arrest Jeong-su. However, Woo-gyeom insists it's too late. Before he can strike, a cop shoots, but Han-jun takes the bullet and begs him to stop.
Woo-gyeom is upset but asks Cha to look after Han-jun. He advances towards Jeong-su, and the cop shoots him again. Woo-gyeom falls off the bridge into the river below. Cha, Han-jun, and Jeong-su are all distraught (for different reasons).
A flashback reveals Director Oh, Assemblyman Baek, and Detective Gong meeting with Chae Jeong-su. Not only does Woo-gyeom find out by following Jeong-su, but Prosecutor Cha does too. It's thanks to Chief Pyo who informs her. When Woo-gyeom escapes, Cha puts her team on catching Detective Gong while she goes after Woo-gyeom. Meanwhile, Director Oh goes through the files Min-gyeong has amassed and realizes they incriminate Jeong-su.
After the altercation at the bridge, Cha interrogates Baek, who remains silent. But she no longer needs him as Oh steps in. He tells her that her father has asked her to stop, hinting that Chairman Cha is behind it all. She refuses and is ready to take down her father if he's involved. Oh decides to cooperate and tell her everything about Cheum.
Woo-gyeom resumes his mother's investigation and finds the personal information of all 223 victims who died from Cheum's illegal experiment. He gives it to Han-jun, who hands it over to Cha. With this intel and Cheum's audit report, Jeong-su is arrested for illegal experiments. Thankful to Woo-gyeom, Cha heads out to pay her respects at his grave, where he is declared dead.
As for Han-jun, he gets his hands on the only sample of the cure hidden in Woo-gyeom's metronome. A flashback shows Woo-gyeom telling Han-jun to do whatever he wants with it. At present, Han-jun is about to throw it in the river when he gets a call from Woo-gyeom. Han-jun smiles on realizing he's alive.
