In the heart of the bustling city of Ahn Hyun, a surge in drug crimes has taken hold, with the capital region at the center of a spreading epidemic. The month's seizures have been significant, prompting a public declaration of a war on drugs by local autonomous groups, aiming to eradicate criminal syndicates. Among these, the Five Spider Gang has become the target of the drug enforcement unit.
On January 22, 2024, during the operation to apprehend the elusive Jang Cheol-gu, a chance encounter occurs in a restaurant. Jang Jae-kyeong, a dedicated police officer, witnesses his old classmate Oh Yun-jin meeting with individuals from Daocheng Chemicals. The conversation revolves around a bribe to quash a report on unpaid wages. Oh Yun-jin, a journalist known for her willingness to accept favors, is caught in a compromising situation, which is overheard in its entirety by Jang Jae-kyeong.
Jang Jae-kyeong's determination to bring Jang Cheol-gu to justice is not solely due to his duty as a police officer but also a personal vendetta. In the past, Jang Cheol-gu had cruelly severed the Achilles tendon of a mutual friend, an act for which Jae-kyeong now exacts retribution by shooting him in the foot, a form of poetic justice.
A month later, despite being subjected to an internal investigation for his actions, Jang Jae-kyeong stands firm in his account of events. His conviction is rewarded with a promotion, and he is celebrated by his colleagues and the bureau chief as a pride of the Anyan drug enforcement team.
However, the night takes a turn when Park Joon-woo, an old acquaintance, approaches Jang Jae-kyeong, reminiscing about a past event and expressing regret for his past cowardice and greed. Park's actions during their high school years, turning a blind eye to injustice, are unforgivable to Jae-kyeong.
Meanwhile, Oh Yun-jin stumbles upon a mother with a drug addiction to a new type of illicit substance. Sensing a scoop, she, as a journalist, is drawn to the story.
On February 24, after a celebratory dinner with his colleagues, Jang Jae-kyeong receives a cryptic text from "Doctor 1882," containing information about a transaction set for February 26. The code "1882" is a distress signal known only to Park Joon-woo and Jang Jae-kyeong. Unable to contact Park, Jae-kyeong is abducted and goes missing for three days.
He awakens on February 26 in a subway station, where he was found by Kim Chang-soo, who received a tip about the transaction. Despite feeling unwell and experiencing a delayed reaction, Jae-kyeong boards the subway to intercept the deal. He spots suspicious individuals but is quickly incapacitated, losing his service weapon in the process.
In a shocking twist, Jae-kyeong discovers the new illicit drug in his pocket and receives a video from 1882 showing his own cravings for the substance, filmed by a woman. Realizing he's been set up, Jae-kyeong must now keep his drugging a secret from everyone.
On the other side of town, a gruesome discovery is made at a construction site, and the unusual presence of a high-profile prosecutor indicates the gravity of the situation. Jae-kyeong later learns of Park Joon-woo's death and, after being taken to the hospital following his collapse, he desperately tries to destroy the blood sample that would reveal the presence of the illicit drug in his system.
This first episode of "Connection" sets the stage for a thrilling crime drama, where personal vendettas, old friendships, and the relentless pursuit of justice collide in a city gripped by the drug epidemic.