Flashback…2008…Spring… Cha Ji Won is thrilled to report to Baek Hee Sung that she passed the police exam. Her dream to become a police officer has come true. She hugs him. Hee Sung assures her he's happy for her.
Ji Won tells Hyun Soo he has one hour to come back to her. Hyun Soo realizes what she's saying. She tells him she misses him. After he hangs up surrounds by thugs, CEO Yeom Sang Cheol agrees to make him a client. Hyun Soo ignores CEO Yeom's offered hand. CEO Yeom shows Hyun Soo the raw material on his laptop. Hyun Soo's eyes widen in surprise.
Ji Won opens the tracker app to find out where her husband is. Recall she put a tracking device in the watch she gave him, which he doesn't know about. Her husband calls and asks where to meet her.
Reporter Kim Moo Jin fixes a light for Do Hae Sue (Do Hyun Soo's sister). She asks why he's helping her. He puts together a floor lamp for her. Hae Sue asks why he's helping her now when he rejected her years ago when she desperately needed his help.
Flashback…A young Hae Sue throws the necklace Moo Jin gave her on the ground and runs away.
Moo Jin notes Hae Sue isn't over the past like she claimed.
Flashback…A young Moo Jin picks up the necklace Hae Sue threw on the ground.
Moo Jin approaches Hae Sue as she stares into the night. He won't apologize for how he acted years ago. Hae Sue doesn't want him to. Moo Jin says he can help her now. Hae Sue maintains she killed the foreman and her brother took the blame. She is sure confessing is the only viable option. Moo Jin doesn't agree. She rushes into her apartment and closes the door. Moo Jin points out he can help her with little things, that he's available. He claims he isn't trying to reestablish their past relationship; he only wants her to know she's not alone.
Hae Sue calls Ji Won. She says she knows that her brother didn't kill the foreman. She promises to reveal what happened on that day when the time is right. She hangs up.
Ji Won is relieved to see Hyun Soo running to her. He's proud to reach her in under an hour. Ji Won's voiceover "I was all you had. Even now, I'm all you have." She examines and finds no injuries. She blurts out that she didn't mean it, she doesn't want to break up, she still loves him. She hugs him. She wishes they could switch bodies so he would understand the depth of her love. Hyun Soo asks what's going on with her. Ji Won hugs him tighter.
Good to see that Hyun Soo has his supportive wife back.
Captain Yoon Sang Pil is taken aback when Team Lead Lee Woo Cheol informs him a human trafficker is a component of the serial murders of Yeonju. Team Lead Lee says he needs time to prove it.
Officer Im Ho Joon reports the woman (CEO Yeom's coworker) survived the surgery. Detective Choi Jae Sub hopes she regains consciousness soon. He gets a call from Oh Bok Ja, the woman that had the photo of Hyun Soo from 5 years ago. Mrs. Oh reports she found a voice recorder left in her home from the night of the attack. In flashback we see the voice recorder fell out of Moo Jin's pocket when Mr. Park hit him on the back of the head.
Ji Won admits she screwed up and a suspect fell and is badly injured. She suggests she quit and they move to the countryside once she's done with this case. Hyun Soo reminds his wife her dream was to become a police officer. He remembers her joy the day that happened. Ji Won claims the job isn't fun anymore. Hyun Soo notes she's acting odd. Ji Won assures him all is well. She walks back into the police station.
At home, Hyun Soo watches his daughter Baek Eun Ha sleep. He murmurs he must go.
In his workshop, Hyun Soo waits for CEO Yeom's call. He demands 100K for the transaction to occur tomorrow.
Flashback…Hyun Soo stares at 3 women tied up in a container. CEO Yeom tells him he can pick one for his first order. Hyun Soo picks the young one. CEO Yeom picks a price. Hyun Soo adds a zero to get the accomplice's name and number. CEO Yeom says this offer is tempting. He gives Hyun Soo a burner phone for their conversations. He warns that if Hyun Soo doesn't follow the rules, he'll eliminate all evidence including people.
The real Baek Hee Sung stares at the family portrait with Hyun Soo as his stand-in. He's surprised the man he hit with his car is impersonating him. His father, Baek Man Woo , informs him that he wasn't expected to live. Hee Sung asks what his path forward is. He promises to follow his father's instructions. He cries that he wants his name and life back. He proposes he meet with the stand-in Hee Sung and make the request. Just then Hyun Soo calls. He asks Mr. Baek for 100K. Mr. Baek wants to know why. Hyun Soo shares he believes he'll be able to learn the identity of the serial killer's accomplice with the money. He shares he knows someone that can help. Hyun Soo points out the this would eliminate the bad press that Mr. Baek despises. Mr. Baek asks him to come to the hospital tomorrow. Gong Mi Ja (Hee Sung's Mother) asks what the stand-in wants. Mr. Baek claims it isn't important.
Mr. Baek puts Hee Sung to bed. He refuses Hee Sung's request to meet the stand-in. Hee Sung believes the stand-in will give him back his life. Mr. Baek believes the stand-in could try and eliminate his son. Mr. Baek tells his son they'll have to be lucky to win.
Hyun Soo wakes and covers his sleeping wife. She's wearing the wedding ring again.
Hyun Soo practices happy expressions in the mirror. He feels something grip his heart. He falls to his knees while he grasps his heart. Hyun Soo exits the bathroom after he regains control. Ji Won rushes to him and says she must go to work; the suspect has died. Hyun Soo asks why she hasn't questioned him about yesterday. Ji Won tells him he can tell her when he's ready. She leaves. Hyun Soo removes his wedding ring and looks stern.
Captain Yoon answers questions from the press. They want to know why a suspect has died.
Team Lead Lee asks the team about the suspect's finances and if anyone is claiming the body. The man with a voice like the accomplice calls Ji Won and informs her he has information about the Yeonju serial murders. The man claims to be Hyun Soo. Ji Won's eyes widen. We see Hyun Soo in glasses and hat talking on the phone. He says he's really Hyun Soo.
Does Hyun Soo is using a voice modulating device.
Detective Choi asks who is one the phone. He takes the phone. The man repeats he's Hyun Soo. Detective Choi doesn't like prank calls. Hyun Soo says he can help catch the accomplice. Detective Choi tells the team this is real.
Flashback…CEO Yeom tells Hyun Soo not to communicate with anyone and allow the money to be verified before his raw material can be picked up. CEO Yeom says he'll give Hyun Soo a photo of the accomplice once he's verified the money.
Team Lead Lee informs Hyun Soo the call is on speaker phone. He's told there are 4 detectives in the room. Team Lead Lee promises to keep this conversation between the team. Hyun Soo says he's recording this call. Hyun Soo says there is a human trafficking ring associated with the Yeonju serial murders. He says this ring supplied the victims that were murdered. Hyun Soo states he'll learn the accomplice's name once he pays for a human. He offers the police a chance to raid. He tells them this is a burner phone. He promises to provide the information to solve the Yeonju murder cases but the police must protect his name and destroy evidence once the murder cases are resolved. Detective Choi can't believe that is all Hyun Soo wants. Hyun Soo states he's not the accomplice and wants to prove that. Detective Choi doesn't believe this is really Hyun Soo. Ji Won asks Hyun Soo to provide the identify of the human trafficker, let them verify it, and they'll believe him. Team Lead Lee promises to do as Hyun Soo wishes when the information is verified. Hyun Soo agrees. He gives them CEO Yeom's name. He warns them CEO Yeom will kill the humans he's trafficking if they slip up. He claims he will too.
Ji Won calls her husband. She asks what he's doing. He claims he's running an errand. She suggests they go out for dinner. Hyun Soo says he has a funeral to attend that evening. She asks him not to go. She cries and says she had a nightmare last night and needs him. Hyun Soo says he must go the funeral. He says he wants to be worthy of her. Ji Won says she'll call him at 10pm. They hang up.
Mrs. Baek takes Hee Sung outside. He relishes the fresh air. He asks how much the housekeeper knows. Mrs. Baek says the housekeeper signed a confidentiality agreement and is deaf and can't read lips. She wants to know who Hee Sung wanted to meet. He says he would have met the woman if he hadn't hit another person. He says that meeting would have changed their lives.
Moo Jin's boss reads his latest article. She wants an exclusive interview with Hae Sue. She asks if Moo Jin is dating his former love again. He says he got rejected. Hyun Soo texts him to meet. He stands to leave.
Hae Sue undergoes hypnosis. She's guided to her father's funeral. She sees herself receiving the accomplices phone number on her arm. She notices his fingernails are too short. She sees a mark on a green bracelet he's wearing. She wonders where she saw it before. She says the accomplice is memorizing her face. She panics. The hypnotist brings her out. She worries the accomplice will try and kill her. The hypnotist suggests she call someone to driver her home. Hae Sue claims she's okay.
The team researches CEO Yeom. He worked at the same facility as Do Min Seok. They learn the suspect worked for CEO Yeom. They start to believe Hyun Soo's information. Detective Choi is excited but says they must catch Hyun Soo too.
Moo Jin drives Hae Sue home. He tells her he'll drive her to future appointments. Moo Jin encourages her to share with her therapists to lighten her fear. Hae Sue asks why Hyun Soo wants to meet. Moo Jin doesn't know.
Officer Im points out they promised to protect Hyun Soo. Detective Choi counters protecting a murderer isn't what the police do. Ji Won has to agree. Detective Choi believes they'll be able to track Hyun Soo's location, take samples of men in the neighborhood, compare to Do Min Seok's DNA and they'll have him. Ji Won doesn't look happy.
Moo Jin is surprised that Hyun Soo called the police with the information about CEO Yeom. Hae Sue says the police can't be trusted. Moo Jin declares the cops will mess things up and CEO Yeom will make him pay. Hyun Soo says he did what his wife would want him to do. He asks Moo Jin to help if things don't work out. Hae Sue wants to help too. Hyun Soo says she's unstable and can't be trusted. He needs someone calm and cool. Moo Jin chides Hyun Soo. Hae Sue is forced to agree she is emotional. Ji Won calls. Hyun Soo uses the voice modulator. The police confirm they believe him. Hyun Soo outlines that he'll provide CEO Yeom the money, then he'll receive the location of the trafficked person. Hyun Soo says if the money is deemed clean, the trafficked person location will be revealed. Team Lead Lee doesn't want Hyun Soo to handle the transaction with CEO Yeom. Hyun Soo insists. Detective Choi claims they can protect Hyun Soo. Ji Won tells him to trust them.
Flashback…Detective Choi tells Ji Won to keep Hyun Soo on the phone to get his location. She refuses to betray Hyun Soo's trust.
Detective Choi, Team Lead Lee, and Ji Won urge him to trust them. Hyun Soo insists they only involve themselves with retrieving the trafficked person.
CEO Yeom talks to the bartender at the bar Hyun Soo and his father visited on the fateful night. He asks about the raw material. The bartender states one person had bad eyesight because of diabetes but the child is okay. CEO Yeom is relieved knowing that is the person Hyun Soo wanted. CEO Yeom asks if Hwang Jung Soon (gang member)) is dead. The bartender confirms it noting they won't have to kill him. CEO Yeom wants to lay low after this transaction. He tells the bartender to load the others on the boat after the transaction is complete. A gang member brings CEO Yeom pictures of the accomplice. CEO Yeom smiles and says the accomplice and Do Min Seok used to be close.
Mr. Baek provides Hyun Soo the money. He's worried this will create problems is things go wrong. Hyun Soo assures him all will be okay. Mr. Baek tells Hyun Soo to disappear and he'll give him 10 times the money. He assures Hyun Soo he'll take care of Ji Won and Eun Ha. Hyun Soo refuses the offer. He doesn't trust Mr. Baek. Hyun Soo points out that Mr. Baek doesn't care about others only his personal goals. Hyun Soo asks if Mr. Baek trusts him. Mr. Baek smiles at his candor. He says their goals are aligned. He wishes Hyun Soo good bye. Hyun Soo leaves with the money.
Captain Yoon doesn't like that Team Lead Lee wants backup based on a tip from an unnamed informant. Team Lead Lee says this will put them closer to solving the Yeonju murders. Captain Yoon declares Team Lead Lee better be right.
The team arms themselves with guns. Detective Choi tells Ji Won she's a good team member. Detective Choi gets a call from stating the audio from Moo Jin's voice recording device Mrs. Oh found has been restored. He doesn't share this with the team.
Ji Won worries about what will happen. She calls Hyun Soo. She tells him she heard the humming recording on the cassette his Walkman in the duffle bag Mrs. Nam gave her. She asks whose voice it was. Using the voice modulator, Hyun Soo shares it was his mother. He says in 1997 his mother went missing but before she went missing, she gave it to him to remember her by. Hyun Soo says the police took his mother's belongings when his father reported her missing. Hyun Soo didn't tell the police about the recording. He shares he was diagnosed as someone that couldn't love or care for other. Ji Won asks why he held onto the recording. Hyun Soo says he doesn't know why he's this way. He says he wants to lie to her. Ji Won tells him to stay safe. She hangs up. Hyun Soo recalls that his wife said she'd call him at 10pm. He looks at his watch. It's 10pm. Hyun Soo knows what that means.
Ji Won remembers the doctor's belief that the recording triggered Hyun Soo's violence. She calls the doctor and yells that the voice recording was given to Hyun Soo by his mother. She points out the doctor interviewed Hyun Soo right after his mother went missing. She barks that Hyun Soo was consumed by his mother's disappearance. Ji Won yells the doctor had a chance to help a hurt and lonely boy but she blew it. She hangs up.
Detective Choi gets the voice recorder. He learns Ji Won also went to the audio engineer with to restore a recording. That surprises Detective Choi.
Detective Choi listens to the recording. It is Mrs. Nam talking about her husband. She notes he gets upset when things don't go as planned. Detective Choi hears Ji Won's voice as she interrupts the conversation between Moo Jin and Mrs. Nam. Next, he hears Moo Jin talking to another man in the car. He doesn't know that man is Hyun Soo.
Team Lead Lee informs his team and the backup team on the protocol for the evening.
Detective Choi hears Moo Jin asks the man how Hyun Soo became Hee Sung. Detective Choi's eyes widen in surprise. He pulls over. Moo Jin asks how the man fooled Ji Won. The man says Ji Won doesn't know about him including his past and his personality disorder. Detective Choi replays the snippet where Moo Jin asks the man how Hyun Soo became Hee Sung. He remembers Ji Won's repeated belief in Hyun Soo. He puts the pieces together.
Hyun Soo prepares to meet CEO Yeom. Moo Jin joins him in the car. Moo Jin chides Hyun Soo for hurting his sister by saying she was unstable. Hyun Soo stands firm that he must protect his sister. Moo Jin asks why Hyun Soo asked for his help. Hyun Soo counters Moo Jin agreed to help. Moo Jin sighs. Hyun Soo points out that Moo Jin agreed because Hyun Soo asked for help in front of his sister and Moo Jin cares what she thinks. Moo Jin is miffed he was manipulated. Hyun Soo says Moo Jin has always been easy to manipulate.
Hae Sue researches the mark on a green bracelet. She finds an image linked to an article on the hospital's overseas volunteer program. She sees the image of the members. Front and center is Mr. Baek. Hae Sue sees a closeup of the green bracelet. She knows it was worn by the accomplice when he gave her the fish charm and his phone number at her father's funeral.
Team Lead Lee tells the team that most likely the trafficked people were never reported missing. Detective Choi burst in the door and tells Ji Won that have to talk. He drags her out of the room. Team Lead Lee and Officer Im follow. Team Lead Lee tells Detective Choi to release Ji Won. Detective Choi tells Ji Won he knows she knew. He asks how she could betray them. Tears fill her eyes.
Hyun Soo remembers Ji Won's request that he stay safe.