In 1990s Gangnam, they ran the streets.
Set in the 1980s, a husband and wife, both detectives, infiltrate a massive criminal organization responsible for the illegal drug trade between Korea, China, and Japan.
Detective Jun-mo goes undercover within Gangnam Union to probe an international drug trade.
Barely passing Gi-cheul's test, Jun-mo joins Gangnam Union and discovers an unexpected truth.
Eui-jeong's appearance puts the squad in trouble. Gi-cheul finds last night's attack suspicious.
The team seeks Eui-jeong's aid to assist Jun-mo in a crisis, which leads to a perilous love triangle.
Earning Gi-cheul's trust, Jun-mo becomes anxious as he sees Gi-cheul making a move towards Eui-jeong.
The delivery accident jeopardizes the trade. Detective Hwang closely surveils Gangnam Union.
Hae-ryun shows interest in Jun-mo and Eui-jeong approaches Gi-cheul. Jun-mo takes an extreme measure.
Gi-cheul suspects Jun-mo. The four people's irreversible decisions trigger the biggest crisis.
The battle with Jae-geon creates a crack. Jun-mo joins forces with Hae-ryun to resume the trade.
Jun-mo and Eui-jeong juggle duty and feelings. Hwang continues to meddle, and the final day arrives.
An accident halts the trade and a crisis approaches as Eui-jeong and Do-hyung worry about Jun-mo.
Gi-cheul and Jun-mo make their way to the final deal. Korea, China, and Japan prepare for the arrest.
