Cast
Ji Sung as Jang Jae-kyung, a detective of the Narcotics Team at Anhyeon Police Station
Jeon Mi-do as Oh Yun-jin, a social affairs reporter of the Anhyeon Economic Daily
Kwon Yul as Park Tae-jin, a prosecutor at Ahn Hyun District Office
Kim Kyung-nam as Won Jong-soo, Geumhyeong Group's successor
Yoon Na-moo as Park Jun-seo, the central figure in the incident
Jung Yoo-min as Choi Ji-yeon, Jun-seo's wife
Jung Jae-kwang as Kim Chang-soo, Jae-kyung's teammate
Cha Yup as Oh Chi-hyun, Jong-soo's chief secretary
Jeong Soon-won as Heo Joo-song, CEO of Two Star Holdings, an insurance company
Park Geun-rok as Jung Sang-ui, a researcher at Geumhyeong Pharmaceutical
Connection: Episode 12 Recap
Yun-ho's attempt to kill Ji-yeon fails, prompting Tae-jin to insist that Yun-ho must be eliminated quickly, as he has become uncontrollable. Jong-soo, Tae-jin, and Chi-hyun start exposing each other's dark secrets and crimes, leading to a fierce argument. During this chaos, Yun-ho calls Jong-soo.
On the call, Yun-ho tells Jong-soo that Tae-jin is the mastermind behind all their troubles and begs for his life. He also tries to create distrust by claiming that Chi-hyun is on Tae-jin's side. Jong-soo puts the call on speakerphone so everyone can hear. Eventually, Jong-soo calms Yun-ho down, agreeing to meet, but instructs Chi-hyun to kill Yun-ho.
Despite Jong-soo's order, Chi-hyun secretly plans to spare Yun-ho, warning him to disappear forever. However, Yun-ho refuses to comply, and Chi-hyun ends up killing him. A hiker witnesses Chi-hyun burying Yun-ho’s body in the mountains.
Meanwhile, Jae-kyung, who is addicted to drugs, struggles to get by with the medication that Yun-jin has obtained for her. He reaches his limit and collapses at home. Worried, Yun-jin enters Jae-kyung’s house using the security code, finds him collapsed, and helps him take a small dose of drugs.
Dr. Sang-ui, a researcher at Geumhyeong Pharmaceutical, under the guise of Prosecutor Tae-jin, reaches out to drug dealer Gong Jin-wook and sets up a meeting with the real Tae-jin. Anticipating a confession, Sang-ui attempts to record Tae-jin admitting to Jun-seo's murder. However, Tae-jin, sensing the trap, cleverly evades it. Instead, he hands Tae-jin a USB drive, telling him to check it out.
Jae-kyung and Yun-jin confront Sang-ui, who takes them to the underground drug manufacturing site at Yeongryun Cold Storage. Sang-ui reveals that he is the Doctor who made the drugs and that he deliberately got Jae-kyung addicted out of personal spite.
Sang-ui explains that he sought revenge for Jun-seo, who had looked after him during their school days. He admits he wanted to avenge Jun-seo’s death by making Jae-kyung suffer, believing that Jae-kyung had taken his only friend and that Jun-seo trusted Jae-kyung more.
Sang-ui confesses everything and states he is willing to face the consequences of his actions, pleading for help in capturing Tae-jin. He mocks Jae-kyung for failing to resolve the situation as he had hoped.
After successfully developing the Pil-o-dong area, Geumhyeong Group Chairman Won Chang-ho plans to oust Tae-jin by promoting him within the prosecutor's office. When Tae-jin asks Chang-ho to reconsider, hoping to work for Geumhyeong Group, Chang-ho reveals he knows about Tae-jin’s involvement in drug dealing with Jun-seo. He declares Tae-jin the greatest threat to the company and refuses to let him join.
In the end, Yun-ho’s body is discovered, and Chi-hyun receives an anonymous tip about Sang-ui meeting Jae-kyung and Yun-jin. Episode 12 concludes with this revelation.