A Russian organized crime group is set out to steal an advanced chemical weapon from Korea and two secret agents are out to stop them. One is a veteran secret agent named AHN Soo-ji who is a master of all forms of martial arts and envied by her comrades. Another is a rookie named LEE Jae-joon who's never been out on the field and always goofs up on the job.
The two agents don't know each other's secret identity. All that they know is that they hate each other. As a couple, Soo-ji and Jae-joon were once a passionate item until Jae-joon couldn't take her lies anymore. But all Soo-ji was trying to do was hide her secret identity.
Nonetheless, the two went on their separate ways and by coincidence bump into each other years later while out on the job. As the two work out their screwy relationship, they go behind each other's backs to fulfill their mission to save the world.