《秘密》的主人公分别是杀人者的女儿、抚养女孩的刑警以及怀揣秘密突然出现的神秘男人，三人在十年后再次重逢而发生的悬疑故事。

Gyun-woo is having difficulty forgetting the sassy girl. He then reunites with his childhood sweetheart, an elementary school classmate from China who was often teased about her broken Korean. They marry despite family opposition, and Gyun-woo has no idea what marriage has in store for him.