A dangerous romance between the Joseon version of a widow hero with a mask and an uptight officer begins.

Three siblings, exhausted by the monotony of day-to-day adulthood, seek to find fulfillment and freedom from their unremarkable lives.

Lee Gang-Doo dreamed of becoming a soccer player, but an accident ended those dreams. His father died in the accident and he broke his leg. Lee Gang-Doo spent 3 years in rehab. Now, he doesn't have anything and just wastes his days. Lee Gang-Doo then meets Ha Moon-Soo. Ha Moon-Soo makes architecture models. Ha Moon-Soo also endured an accident that killed her younger sibling. She has suffered from guilt that she survived. She has lived her life earnestly, while suppressing her feelings. After meeting Lee Gang-Doo, Ha Moon-Soo begins to express her hidden feelings.

In modern society, there are people who are neglected and suffering. They are often involved in unfortunate events, such as industrial accidents, and end up dying. Most of the disasters could be prevented in advance with little attention. However, some companies or public organizations tend not to prepare for potential accidents because of the high cost. That’s how industrial accidents take place. Doctor Detective is a drama where medical doctors treat the patients suffering from industrial accidents and look into the truth behind the accidents. The story of the drama starts when Joong Eun, who is an enormously talented medical doctor, gets to join an undiagnosed disease center(UDC) in the middle of experiencing difficulties in her personal life. And she starts to look into her patients' diseases caused by industrial accidents and work on revealing the truth concealed by those with power.

Hyo-joo (Ha-neul Kim) is a temporary teacher at a boys' high school and Hae-yeong (In-yeong Yu) is a fellow teacher who is the school board chairman's daughter. One day, Hyo-joo witnesses Hae-young locked in a passionate embrace with a boy and she starts feeling an inexplicable sense of humiliation towards Hae-yeong.