A female detective uses her keen observation and acute reasoning to solve cases, bring judgment to criminals, and defend the wrongly accused. As she exposes the ugly sides of human nature, her fierce hatred of crime makes her the investigator society desperately needs.
At National Forensic Hospital, an inmate, a woman who is known to have killed her own daughter, has gone missing. However, all the staff members at the hospital claim that they have thoroughly checked the number of inmates and that they have absolutely no idea where and when she has gone missing. Detective Han Tae Gyu is put in charge of investigating the situation and gets into a dispute with Ms. Kang.
The police go to Ms. Ma's house and make her husband, Jang Cheol Min, call her in order to trace her location. While talking on the phone, Cheol Min warns her not to come home just before getting subdued by the cops. Meanwhile, Ms. Ma visits the charnel house to see her late daughter, Min Seo.
During a flashback while Ms. Ma is being interrogated by Tae Gyu and Prosecutor Yang, she claims that although she had wanted to keep her daughter by her side, she did not kill her. In addition, she claims that a long-haired woman in a white hanbok has told her that she saw the killer. However, the police think that the long-haired woman is just a ghost and do not believe her.
The inmate that has run away from the hospital now lives at Rainbow Village while being disguised as a mystery novel writer, Ma Ji Won. One day, she tells one of her neighbors that her husband has a mistress. Three of the ladies gather together and go find the woman who is having the affair.
Thanks to Eun Ji's help, Ji Won scrapes through the situation where she could get caught by the detective Tae Gyu in front of her neighbors. However, she still doesn't know who Eun Ji is and why she offers help. After the ruckus, the residences in Rainbow Village start to get blackmailed. Meanwhile, a young boy called Woo Joon comes to visit Ji Won and asks about a bag.
Eun Ji finds out that Ji Won is looking for Actress Lee Jung Hee and says she'll help find the actress. They get to find some photos online that seem to be taken in Rainbow Village and follow where those photos lead. They end up in an empty house and find a man dead. In a doubt that the dead man has something to do with Lee Jung Hee, Ji Won visits her to ask about him.
The suicide note left by Ms. Park makes Ji Won curious. Eun Ji tells her to drop the case, but Ji Won is worried about Woo Joon. Tae Gyu thinks that the wrong person could've been locked up for nine years and wishes to undo the mistake he made.
The death of his mother is too much to cope with for Woo Joon, and Ji Won pities him. Although she is certain that the real murderer hasn't been caught, she feels helpless without any solid proof. Eun Ji suggests setting up a trap.
During a flashback, Min Seo is seen waiting for her dad and gets kidnapped while her teacher is away. The kidnapper asks for one million dollars, and Ms. Ma prepares the money and goes to the designated spot, only to meet a woman in a white hanbok. Meanwhile, Director Sung Jae Deok and his wife and actress, Lee Jung Hee, move into the neighborhood.
Ji Won visits Choi Man Sik who is currently incarcerated. He tells her that if she takes care of Woo Joon until his sister comes, he would tell her an interesting story. He then goes on to talk about the very case nine years ago when a woman, Ji Won, was convicted of smashing her own daughter's face with a rock.
Ji Won goes to Lee Jung Hee's house to interview her. During the interview, she asks the actress about the night nine years ago when she was in the woods while shooting “Shaman”. However, Jung Hee says some strange things. Ji Won tells Eun Ji that she's positive that something happened to Jung Hee on that day.
During Jung Hee's housewarming party, Bae Hee Jae is found dead. Eun Ji calls Ji Won immediately to report this, and Ji Won tells her that no one should leave the house as of now since the murderer is still in the house. Furthermore, after hearing that Hee Jae was spotted drinking wine, Chang Gil suspects that someone has put poison into the glass.
After drinking a cup of coffee and collapsing, Jung Hee is taken to a hospital. Chang Gil gets the coffee's components analyzed and finds traces of arsenic in it. However and strangely enough, the police are not starting an investigation. Meanwhile, So Jung asks Ji Won whether she has broken out of jail before.
Ji Won tells Jae Deok, Jung Hee's husband, that someone is purposely trying to harm Jung Hee and that this person may be the culprit from the murder incident Jung Hee witnessed nine years ago. One morning, Jung Hee finds a bloodied doll on her bed and is sent back to the hospital due to shock. Jae Deok calls in Ji Won and asks her if she thinks the culprit is back for her.
During the investors' meeting regarding the movie, Cheol Min attends the gathering as an investor himself alongside Tae Gyu. Thanks to Eun Ji's intervention, Ji Won is able to flee without being noticed. Meanwhile, upon seeing Eun Ji, Jung Hee breaks down and tells her husband that she had witnessed the murder nine years ago.
Mal Goo shows Ji Won a broken, fake nail that he found at the place where the rock was lifted from. He asks her to accompany the president whom he has been taking care of while he looks into it with Eun Ji. While talking with the president, Ji Won's cover gets blown as he claims that the Ma Ji Won he knew from back then is different from the person sitting next to him at the moment.
In order to figure out what exactly happened nine years ago, Tae Gyu goes to the spot where Min Seo was found. Now that Myung Hee is dead, Ms. Ma must find another lead. Jae Deok asks Jung Hee if she killed Myung Hee.
Eun Ji thinks the photographer who took pictures at the housewarming party might be holding a clue. Ms. Ma and Eun Ji pay a visit to the studio and find a lead. Meanwhile, Jung Hee decides to pay the person who has been blackmailing her.
Yoo Jung, or Ye Ji, does what she has to do in order to protect her mom. Ms. Ma and Eun Ji arrive at the scene later, only to find Joong Chul dead. While Ms. Ma is trying to figure out who the real culprit is, Eun Ji is up to something.
After seeing Woo Joon, Ms. Ma figures out everything. She rushes to Yoo Jung's studio, thinking that Eun Ji is in danger. She tries to persuade Yoo Jung to stop killing people.
The real Ma Ji Won hears about the murder cases that have been solved in Rainbow Village. She decides to pay the fake Ji Won a visit so that she can get inspirations for her writing. Meanwhile, Eun Ji meets up with Tae Gyu.
The ladies from two villages start the game of Mafia. The real Ma Ji Won decides to join as well. However, the game takes an unexpected turn before it even begins.
The police takes the real Ma Ji Won to the station and tries to run a fingerprint test on her. Eun Ji tells the fake Ma Ji Won that her husband had an accomplice. The real Ma Ji Won suggests a bet on who catches the murderer first.
The fake Ma Ji Won agrees on the bet to find the murderer. The real Ma Ji Won becomes certain that Jo Ye Jin killed Ahn Seong Tae, since she has a clear motive to kill Do Ja Yeon. The only thing she needs to find is the evidence.
Cheol Min receives a text message from his wife. It implies that his wife took her own life out of distress. Tae Gyu starts investigating the case and soon comes to a realization.
Eun Ji finds out that the real Ma Ji Won got murdered by Cheol Min's accomplice. She fails to convince the fake Ji Won who still has trust in her husband. She must protect her from the people who want her dead.
A dead body gets found at the precinct station, but the security camera installed at the station was broken and failed to record anything during the time of death. Meanwhile, Eun Ji gets to meet the man who kidnapped her little sister.
Tae Gyu gets closer and closer to the truth. Meanwhile, Ms. Ma senses something strange while interviewing the people related to the recent murder. After solving the case, she realizes something.
When Woo Joon gets hurt, Ms. Ma decides to take action. She leaves Woo Joon to Ms. Hong and promises her that she will be back soon. She confronts Yang Mi Hee in person and lets her know who she's dealing with.
Mi Hee tells Cheol Min that his wife is still alive and that she knows everything. Cheol Min panics and gets in an argument with Mi Hee. Meanwhile, Ms. Ma looks for evidence to fight them with.
Ms. Ma manages to escape and take Jang Sun Doo with her. Mi Hee tells Cheol Min to act as if he doesn't know anything so that she can use him as bait. Although Ms. Ma knows that it's a trap set up by Mi Hee, she knows that time is running out.
Eun Ji manages to find evidence that can help Ms. Ma. However, Cheol Min breaks free and takes Eun Ji with him. Mi Hee calls Ms. Ma and demands her to hand over all the evidence she acquired.
