Eun-soo is a housewife, who struggles to pay for her husband’s medical expenses. He is terminally ill. Eun-soo becomes entangled in a bag of drugs with a teacher named Yi-kyeong. He is a mysterious figure. Eun-soo and Yi-kyeong are chased by veteran detective Tae-gu.
A mermaid from the Joseon period ends up in present-day Seoul, where she crosses paths with a swindler who may have ties to someone from her past.
Lee Yool falls off a cliff and nearly dies in an attempted assassination. He loses his memory, and wanders for 100 days under a new name and personality. During this period, he meets Hong Sim, head of the first detective agency in Joseon.
