Episode 3 recap: A series of replicants were killed, and Cheng Nuo found Lv Yan.

Cheng Nuo and An Qiu arrived at the old street, a place filled with a mix of people from all walks of life, appearing chaotic. Cheng Nuo suddenly chased after someone he saw, and An Qiu, unaware of what was happening, followed suit. However, Cheng Nuo didn't find the person after running out of the street. Instead, they heard that a replicant had been killed on the street. They hurriedly went to investigate and indeed found a replicant's body arranged in a peculiar manner. People on the street mentioned that there were more deceased replicants nearby. Cheng Nuo and An Qiu rushed over and discovered more replicant corpses.

Minister Fang came looking for Cheng Nuo, and An Qiu informed him that she didn't know where Cheng Nuo had gone. She mentioned that during their investigation of replicants in the old street earlier that day, Cheng Nuo saw someone named Lv Yan but couldn't catch up to them. An Qiu also noticed a significant change in Cheng Nuo's demeanor.

Minister Fang informed An Qiu that Cheng Nuo's mother, Zhang Ya, was a researcher at Mingmou and that Lv Yan was her partner. However, Zhang Ya had committed suicide by jumping off a building a year ago, and her final phone call was to Lv Yan. Lv Yan disappeared since that time.

An Qiu and Cheng Nuo discovered that all four cases they encountered involved the deaths of replicants. After killing a replicant, the perpetrator left behind a binary star astrological chart at the crime scene, arranging the murder in the same ritualistic manner each time. The consistent modus operandi indicates a serial killing spree. Cheng Nuo added that all these cases were also connected to the old street. While Chen Xin Hui seemed unrelated to the old street, the replicant she purchased should be connected to it.

Cheng Nuo and An Qiu went to the old street to investigate relevant clues but found nothing useful. That is until they encountered a boy named Yi Hang, who had a fondness for drawing. However, he refused to answer any questions and merely repeated their inquiries. When it came to his artwork, he spoke up. Cheng Nuo noticed Lv Yan's figure in Yi Hang's drawings and couldn't contain his urge to interrogate the boy. Yi Hang became frightened and started screaming, prompting his mother to come and angrily demand Cheng Nuo to leave. Taking advantage of the situation, Yi Hang vanished.

An Qiu pulled Cheng Nuo away, but Cheng Nuo was frustrated, believing that An Qiu had hindered his search for the truth. An Qiu professionally deduced that Yi Hang had severe autism. Yi Hang's mother told An Qiu that for some unknown reason, Yi Hang always included himself in every painting he created.

Cheng Nuo noticed that Yi Hang was drawing on a utility pole, depicting scenes from the crime scenes. He shook Yi Hang frantically, but An Qiu arrived and desperately tried to stop Cheng Nuo. She explained to Cheng Nuo that this was a gift of autistic children—their exceptional ability to mimic.

An Qiu believed that Cheng Nuo now had an obsession. He wasn't just investigating the case, but also trying to uncover the cause of his mother's death. Cheng Nuo was struck by An Qiu's words, murmuring that he just wanted to know if his mother's death was related to him. Zhang Ya was often busy with work, and studying replicants was her most dedicated endeavor.

Cheng Nuo often felt neglected by his mother. He studied hard, hoping to gain his mother's attention. But even when he eventually got accepted into MIT, his mother only casually mentioned that she already knew he would get in. Zhang Ya's indifferent attitude stung Cheng Nuo, and in a fit of anger, he tore up the acceptance letter and joined Mingmou Institute.

When Zhang Ya found out, she didn't express much surprise or anger. She simply said that he had grown up and could make his own decisions. Cheng Nuo was thoroughly provoked. He knew Zhang Ya had a strong attachment to replicants, so he deliberately started picking fights with them. When Zhang Ya found out, she blamed Cheng Nuo for his irrational behavior. In a moment of impulsiveness, Cheng Nuo suggested that since Zhang Ya cared so much about replicants, she should just find one to be her son.

That's when Zhang Ya jumped off the building. An Qiu found a necklace at the crime scene with the name "Xia Keyu" engraved on it. Cheng Nuo recognized it as something Lv Yan left behind because Xia Keyu was Lv Yan's wife. They deduced that Lv Yan would come back to look for the necklace, so they waited nearby, hoping to catch him. They kept watch all night until Lv Yan finally appeared the next morning.

Cheng Nuo and An Qiu followed him, and to their surprise, they discovered three children at his residence. When Lv Yan returned, Cheng Nuo grabbed him in anger. But Lv Yan insisted that he didn't kill the replicants. He then began recounting his relationship with Zhang Ya. Dr. Zhang Ya established the replicant research lab to use psychological intervention to eliminate replicants' obsessions and help them better integrate into human society.

Thus, Lv Yan brought replicant data to the lab and became Zhang Ya's assistant.