In the occupied Joseon of 1926, a handmaiden named Soo-a worked for a Japanese collaborator. While discovering an injured activist named Eui-hyeon at the beach, Soo-a felt an immediate connection and nursed him back to health. After hearing Eui-hyeon’s tale of the "Little Mermaid" saving a prince from his death, Soo-a was determined to reunite with Eui-hyeon. However, she was unaware of the tragedy that awaited her in her quest to be with him.