In Gyeongseong, the city of glittering lights and glamorous desire, Gyeongseong Detective Agency has opened its doors at No. 45, District 1, Myeongchijeong. Sohwa, a 16-year-old servant girl, has nothing to her name but her wits and bravery. When she accidentally gets caught up in a secret scheme, she meets Jeong Haegyeong, a young man running his own detective agency. Chased by memories from the past, they must work together to clear her name.