How can a mermaid from the Joseon era survive in modern society? Sim Chung is a mermaid who follows her one true love, a nobleman’s son named Kim Dam-Ryung from the Joseon Dynasty, to modern-day Seoul. Dam-Ryung’s modern doppelgänger is Heo Joon-Jae, a highly skilled scam artist who first becomes interested in Sim Chung because of a jade bracelet worth $6 million that Sim Chung wears. With nowhere to go, Sim Chung is taken in by Joon-Jae, who also finds his con partners, Jo Nam-Doo and Tae-O, hiding out in his home from a vengeful past victim of their scams. Sim Chung discovers a rival for Joon-Jae’s heart in Cha Si-A, a researcher at KAIST who deals with ancient artifacts. When a dangerous killer named Ma Dae-Young, sent by Joon-Jae’s stepmother who wants to make her own son the heir to Joon-Jae’s fortunes, can Sim Chung survive her strange new environment while also helping Joon-Jae avoid the dangers that await him?