Ace NIS agent Jung Hae-seong is demoted after a mission failure. He goes undercover at a high school to locate King Gojong's missing gold, meeting his teacher Oh Soo-ah, who sees him as her lost first love, stirring old heartbreak.

Cast: Seo Kang-joon, Jin Ki-joo, Kim Shin-rock, Kim Min-ju, Yoon Ga-i, Kim Young-ah