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
Jae-kyung and Yun-jin discover that Lee Myung-guk was a senior member of their high school club, Audiophile. However, their joy is short-lived as Jae-kyung struggles with drug withdrawal symptoms and eventually succumbs to the urge, to take drugs that had been confiscated by the police as evidence.
In an attempt to erase footage of himself stealing the drugs from the police station, Jae-kyung reviews the CCTV recordings, only to find that the video from that time frame has already been deleted by someone else. The duty officer informs him that Inspector Kim Chang-soo was the one who visited earlier.
When a team member reports the missing drugs, Jae-kyung hides the fact that he stole and used them. Instead, he harshly blames the team member and covers up the evidence.
Joo-song receives a call from Choi Ji-yeon and decides to visit her. He asks Yun-jin to accompany him, but she declines, saying she’s busy. Ji-yeon, Jun-seo’s wife, believes that her husband left the insurance money to his former friends, reporter Yun-jin and police officer Jae-kyung, who are not close right now, to uncover the truth behind his death. She asks Joo-song to keep her updated on any developments.
Gong Jin-wook is permitted by the Doctor to make contact only once after midnight if an urgent issue arises.
Then comes the shocking revelation: Ji-yeon is having an affair with Prosecutor Tae-jin, Jun-seo's close friend.
For his investigation into Jun-seo's death, Jae-kyung checks the CCTV at a mill near the construction site where Jun-seo died. While Jae-kyung steps away for a moment, Jeong Yun-ho, a taxi driver who is one of the "Inner Circle" friends, breaks in, kills the mill owner and destroys the evidence. Jae-kyung returns just in time to receive a CCTV backup from the dying owner, concluding episode 4 of "Connection."
