Season 1 of Decoy premiered on January 27, 2023.

Eight years ago, Noh Sang Cheon, the mastermind of a financial fraud scheme that duped tens of thousands of South Korean victims into investing billions of dollars' worth of their savings into a bogus project, went on the run. He attempted to evade the law by escaping to China and the nation was rocked when news of his death broke. Now, almost a decade later, a justice-loving police detective named Goo Do Han makes a startling discovery.

In the course of investigating a domestic murder case, Goo Do Han finds evidence implicating Noh Sang Cheon as a suspect. How could it be that this fraudster—thought to have died years ago—is linked to the case? It falls to Goo Do Han to try to determine if Noh Sang Cheon is actually dead or not. If he is dead, who could the real murderer be? If not, where was Noh Sang Cheon hiding all this time? As the detective continues to investigate, he begins to wonder if there might be a link between the fraud of eight years ago and the mysterious murder.

Season 2 of Decoy premiered on April 7, 2023.

Just under a decade ago, South Korea was shaken to the core by a financial fraud project. Thousands of unsuspecting victims were tricked into investing their life savings. After the project was exposed as a scam, its mastermind Noh Sang Cheon ran away to China in a bid to escape the police. But he was soon after reported to have died in mysterious circumstances. The trail went cold. But some eight years after he was reported dead, the evidence appears to suggest that the notorious fraudster is still alive! A spate of killings begins, with Noh Sang Cheon apparently linked to the deaths.

Trying to piece together the truth is the police officer and former lawyer Goo Do Han. Also on a quest for truth is a reporter named Cheon Na Yeon. She believes that a number of the murders have been covered – and that police investigations into the death may have been botched. The stakes begin to rise as games become deadly.