The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.

Set in the 18th century, the drama depicts the love story between King Jeongjo and royal concubine Seong Uibin.

Hiding a twisted past, a man maintains his facade as the perfect husband to his detective wife — until she begins investigating a series of murders.

After a series of unfortunate events, Mok Hae-won quits her job in Seoul and goes back to Bookhyun Village, in Gangwon Province, where she briefly lived when she was in high school. There, she meets again her former classmate and neighbor, Im Eun-seob. He also came back to Bookhyun after leaving the village for a few years and now owns a bookstore.

The Subway Police of Wangsoori Station is led by Chief Inspector Ko Ji Seok. He is the best of the best, although his only goal in life is to have a stable, uneventful career. However, a serial killer, nicknamed "the Subway Ghost", strikes the Subway Police 30 Year Anniversary event. An applicant shows up for a job interview to join the team.