A Russian organized crime group takes possession of an advanced bio-chemical weapon from Korea with the help of a corrupt Korean scientist, and two special agents are the world’s only hope to stop them. One is a veteran domestic secret agent named Ahn Soo-ji (Kim Ha-neul) who is a master martial artist and fencer. The other is a rookie international agent named Lee Jae-joon (Kang Ji-hwan) whose foundation in analytical work, rather than field work, gets him into trouble when he consistently goofs up on the job. The two agents have an ill-fated relationship, when coincidentally they are dating and don’t know each other’s secret identities. The passion between them turns to madness, as the lies and secrets between them build until they nearly kill each other. The only thing they can trust is the fact they love and hate each other. The tension builds as they attempt to work out their relationship, while working behind each other’s backs, unknowingly on the same mission to save the world.