Ma Yi Deum is a competent prosecutor who gets her job done. One day, she witnesses her superior harassing a news reporter. In return for personnel appointment, Yi Deum gets offered a case. However, things start going south when Yi Deum meets a newly appointed prosecutor, Yeo Jin Wook.

Yi Deum gets appointed to the most unwanted department of all, Crimes Against Girls Unit. There, she reunites with Jin Wook. Furthermore, the two become tenant and landlord which gives Yi Deum even more of a headache. Together, they become in charge of an attempted rape case.

Despite the win, Jin Wook criticizes Yi Deum about the way she was not considerate of her client. Ms. Min of CAGU also scolds her for the way she won. While working on another case together, Jin Wook and Yi Deum's different investigative methods make them drift apart more.

Yi Deum becomes shocked when she finds a hidden camera in her house. With every other piece of evidence damaged, the video of Yi Deum is the only thing they have left as evidence. Yi Deum wants to hide it while Jin Wook wants her to hand it over.

When Yi Deum comes to work after the hidden camera case, she shows everyone that she is not intimidated. Jin Wook finds out that the girl he treated five years ago became involved in a case. Shocked, he asks for Yi Deum's help. The two work together to find out what really happened.

While rescuing the victim, Yi Deum takes a knife for Jin Wook. Gap Soo tries to use the hospitalized Yi Deum for his political agenda and gets in a conflict with Ji Sook. While taking care of Yi Deum, Jin Wook finds out what happened to her mother.

Yi Deum gets her hopes up thinking that her mother might be alive. However, her hopes become shattered once again. When Jin Wook sees how down Yi Deum is, he tries to cheer her up in his own ways.

Yi Deum finds out that Gap Soo's sexual torture incident is related to the missing of her mother. When Jin Wook senses that his mother is hiding the truth from him, he becomes anxious. Worried for Yi Deum, Jin Wook goes to her.

When Soo Ah is found dead, Yi Deum and Jin Wook become devastated. They bring in two suspects that each claims the other one to be the real perpetrator. Meanwhile, Jin Wook finds out the truth behind the missing Kwak Young Shil.

In order to save his brother, Sang Ho cuts a deal with Yi Deum. Through that, Yi Deum learns about the secrets behind her mother. She plans to take revenge on Gap Soo.

While looking for ways to make money, Yi Deum runs into someone that needs legal advice. She decides to defend the accused of a quasi-rape case. When the case goes to court, she meets Jin Wook as the prosecutor.

Gap Soo's spokesperson gets pinned down as the suspect for a sexual assault case from 20 years ago. Yi Deum gets herself involved in the case as an attorney. Together with Jin Wook, she works on the case.

Yi Deum and Jin Wook acquire a video clip that points Tae Kyoo as the true culprit. They come up with a plan to expose Kingdom and the dirty deeds that take place there. Meanwhile, Ms. Min requests for a warrant to be issued so that they can search Kingdom.

Gap Soo finds out that Yi Deum's mother is alive and gives orders to get rid of her. Together with Jin Wook and Ms. Min, Yi Deum forms a special investigation team to bring down Gap Soo along with Kingdom.

Young Shil learns about her forgotten past. Cornered, Gap Soo makes a dangerous proposal to Yi Deum. When Jin Wook becomes aware of this, he anticipates Gap Soo's next move.