In the civil war between North and South Korea, the tension within was high, especially when a mission was hooked with national secrets. A black box, hence, because the key to the struggle. Success, would never come so easily. However, amid the brutal fight for the key-the black box of a crashed battleplane, the male and female spy from the two different nations fell in love with each other. They helped each other secretly, in order to complete their corresponding mission, for the sake of loyalty - and love.

However, a fatal plane crash of battleplane occured and finally they sacrifice their valuable love and lives for the peace of human world.