Flashback…Baek Hee Sung is designing and fashioning rings when Cha Ji Won enters. She snaps a photo of him. He demands she delete. Ji Won does so. Hee Sung asks why she's so inquisitive about him. She takes a drink for courage, then tells him she likes him. Hee Sung is surprised. He's fixated by something else. He tells Ji Won not to come back. She's taken aback.
The front door opens and a man in a hooded raincoat enters the apartment. He pulls back the hood and reveals his face. Hee Sung and Ji Won stare at each other as the lighting flashes outside. Ji Won asks where her husband was. Hee Sung lies that he couldn't sleep and worked in his studio. He brings beer. Ji Won pulls a can of beer out of the bag and smile. She remembers the day she confessed and he kicked her out. Hee Sung acts embarrassed. He admits he felt awkward. They banter.
Underneath Hee Sung's studio. Reporter Kim Moo Jin is bound and gagged.
Flashback…Hee Sung feeds Moo Jin. Hee Sung says this will be his last meal. Moo Jin pleads with his old high school classmate Hee Sung . Hee Sung crushes sleeping pills he got from his mother and dissolves them in water. Moo Jin refuses to drink. He yells for someone to help him but no one can hear him. He yells that the serial murderer Hee Sung is here. He begs Hee Sung to spare his life. Hee Sung tells Moo Jin read out loud a post he wrote in 2011 where he says he was an unwitting party to a murder. Hee Sung asks if this was Moo Jin's story. Hee Sung asks if Moo Jin has a video associated with the murder. Moo Jin swears he won't tell anyone. Hee Sung doesn't care about Moo Jin's word, he wants leverage.
A crowd gathers around Mr. Nam's eatery. They wonder who was killed. Ji Won and Officer Im Ho Joon arrive at the scene. A dog leash is around Mr. Nam's throat. Ji Won knows this was the special trait from the serial murders in Yeonju that the public does not know about. She asks Detective Choi Jae Sub if the victim has missing nails. Detective Choi reports 2 nails are missing. He points to the CCTV camera. At the station the CCTV shows a man in a hooded raincoat commit the murder. Ji Won remembers Hee Sung wearing a similar hooded raincoat last night. They discuss the similarities and differences of the killings. The chief worries this is a serial murder case. Captain Yoon Sang Pil (Lim Chul Hyung) doesn't want another department to handle it. He asks Team Lead Lee Woo Cheol if his team can investigate and close the case. Team Lead Lee believes they can catch the killer. He thinks the killer was reckless in choosing this victim and a clue can be found.
Detective Oh reports the last person the victim spoke with via his cell was Moo Jin. Ji Won says she knows and met with Moo Jin just last week. They learn Moo Jin called the murder victim yesterday. Team Lead Lee orders the team to find Moo Jin.
Moo Jin spies a piece of broken glass and tips his chair get it.
Hee Sung enters Moo Jin's apartment. He finds Moo Jin's laptop just as promised. He logs in and goes to the secret folder. The video is in the folder.
Video flashback…high school Moo Jin and his friends are outdoors for an art class.
Ji Won and Moo Jin visit Moo Jin's boss. She says he didn't have to report in for a couple of days. She says he often turns his phone off. The secretary wonders if Moo Jin locked himself in the bathroom again.
Video flashback…Moo Jin follows high school Hae Su to her art studio her father built her. She presses Moo Jin to model for her.
Hee Sung murmurs that Moo Jin lied. He hears a knock at the door. He looks through the peep hole. It's his wife, Officer Im, and fire patrol. Ji Won has the fire patrol open the door. They search but the apartment is empty. Ji Won sends the fire patrol home. She calls Moo Jin's phone. It goes straight to voicemail. Ji Won feels the laptop. It's warm. They agree someone was just there. They search the apartment for someone hiding. Ji Won finds a turned over plant. Hee Sung is precariously perched outside the balcony and the building. The sun goes behind the clouds eliminating Hee Sung's shadow. Ji Won looks out the balcony and sees no one. Hee Sung slips and hangs on for dear life. Ji Won approaches the side of the balcony where Hee Sung hides outside. She pulls back the blinds. Hee Sung presses himself into the building. Officer Im calls to Ji Won and she rushes to answer her phone. It's Hee Sung saying that Moo Jin is at the studio. She asks to speak with him. Hee Sung lies that Moo Jin went to his car to charge his phone. Ji Won asks Hee Sung to tell Moo Jin to come to the police station. A young child sees Hee Sung perched outside the balcony. He yells. Ji Won hears the yell. Hee Sung distracts her by saying he's not feeling well. Instantly concerned she tells him to rest. He tells her he'll turn his phone off. The child's mother arrives and asks what is wrong. The child points to the balcony but Hee Sung is gone. Ji Won and Officer Im leave the apartment. Hee Sung reenters the apartment relieved he wasn't caught.
Detective Choi and Detective Oh view CCTV. They spy the man in the hooded raincoat getting into a taxi after the murder.
Hee Sung returns to his studio. He unlocks the padlock to the basement. Moo Jin attacks. Hee Sung defends himself. Moo Jin hits Hee Sung calling him a monster. Hee Sung gets the advantage and starts to strangle Moo Jin.
Ji Won is worried about Hee Sung and tells Officer Im she is going to check on her sick husband.
Detective Choi tracks down the taxi driver and asks him to come to the station. Officer Im arrives at the station. He asks if Moo Jin is there yet.
Ji Won finds a client outside her husband's studio. She asks if everything is okay as the studio is often closed. That surprised Ji Won. She enters the studio and find Hee Sung exiting. They are startled to see each other. She notices the bruise on his face. She surprised again when Moo Jin exits the studio. He asks if she came to pick him up.
Flashback…Hee Sung's studio basement…Hee Sung releases Moo Jin who says Hee Sung won't be able to get away with this. Moo Jin declares his death will cause a ruckus. Hee Sung admits he can't kill Moo Jin while the police are searching for him. He tells Moo Jin to head to the police station after he tidies up. Moo Jin chuckles that now he has some power. He calls Hee Sung a psychopath. He wants an apology. Hee Sung counters they don't have time. Moo Jin warns Hee Sung he can make trouble. Hee Sung notes the video he watched gives him an edge. Moo Jin is taken aback.
Flashback…Moo Jin's apartment…Hee Sung wonders where the video footage is that wasn't on Moo Jin's laptop. He searches. He finds a camcorder with video from high school days. While recording, Moo Jin finds a lair.
Flashback…Hee Sung's studio basement…Hee Sung warns Moo Jin the video he found could destroy him. Hee Sung says if Moo Jin had made a different choice that day, a serial murder would have stopped. Hee Sung asks how many died because of him. Hee Sung ask if the video excited him. Moo Jin declares he's not a monster. Hee Sung suggests they help each other live or they'll both die. Moo Jin agrees. Hee Sung asks for an apology. Moo Jin sighs.
I like how Hee Sung repeats other's words to their face.
Ji Won tends Hee Sung's face. Irked, she arrests Moo Jin for assault. Moo Jin looks pleadingly to Hee Sung who admits he started the fight. Ji Won declares Hee Sung is too kind. Moo Jin rolls his eyes. Hee Sung says Moo Jin pressured him for free jewelry in return for a favorable article about the shop. He got angry and punched him. Ji Won glares at Moo Jin who notes this only reinforces her bad opinion of him. Hee Sung apologizes. Moo Jin can't believe it. Ji Won points out the victim apologized first. She demands he do the same. Moo Jin apologizes. Ji Won makes sure her husband is okay. Moo Jin asks why she wanted to see him. She reveals Mr. Nam was murdered last night. Moo Jin looks at Hee Sung.
At the police station Moo Jin listens to the voicemail from Mr. Nam who stated he knew something of interest. Hee Sung helped his father commit the murders. Moo Jin realizes that the food Hee Sung brought him last night was from Mr. Nam's eatery. They hear the murderer enters the room and Mr. Nam yell in surprise. The police point out that Mr. Nam knew his killer. Ji Won wants to know who Hee Sung is. Detective Choi declares catching Hee Sung is the obvious next step. Moo Jin shares that Hee Sung is the serial killer's Do Min Seok, son. He says he wrote an article about them. Officer Im remembers Hee Sung killed a village foreman then fled town know that his father was dead.
Flashback… Yeonju…the police find Hee Sung's backpack which contained the murder weapon.
Detective Choi notes 18 years later, no one has caught Hee Sung. Team Lead Lee asks the connection to Mr. Nam. Moo Jin says that Mr. Nam called him about the article. Ji Won asks about the statement that Hee Sung helped his father murder. Moo Jin says that Hee Sung was an odd person. Moo Jin says he has a revenge-oriented antisocial personality disorder. Noticing the verb tense, Ji Won asks if Moo Jin knows Hee Sung in the present. Moo Jin lies he meant that hearing about Hyun Soo after all these years was a surprise. Officer Im gets a call that Mr. Nam's wife is awake.
Ji Won and Officer Im go to the hospital to speak with Mr. Nam's wife. Ji Won asks her husband had any enemies. She says that Hyun Soo called her husband daily.
Detective Choi interview the taxi driver. He reports the man in the raincoat had him wait 30 minutes then he had the taxi driver drop him off in a particular neighborhood. Detective Choi asks if the taxi driver lives alone. The taxi driver confirms this. Detective Choi asks for anything else the taxi driver can do. The taxi driver says the man said he did similar work to his father.
Baek Eun Ha (Jung Seo Yeon) (Hee Sung's daughter) notices her father is smiling. She asks why.
Moo Jin returns to his apartment to find the video missing from the camcorder confirming Hee Sung has the video. He sighs. He's relieved to be home and alive. He wonders if Hee Sung kill Mr. Nam. He thinks about reporting his knowledge but hesitates for fear of retaliation from his boss. That line of thought is interrupted by a call from his boss.
He meets his boss for coffee. She's pleased with him because he knows exclusive details about Mr. Nam's death. Moo Jin downplays the knowledge claiming coincidence. Then the time of the murder strikes his memory.
Flashback…Hee Sung's studio basement…On the night of Mr. Nam's murder, Hee Sung tells Moo Jin he wants collateral from him. The clock strikes 3am.
Moo Jin believes Hee Sung isn't the murderer. He tells his boss he way indeed be able to write an exclusive.
Ji Won and Officer Im stand in an eatery. She sees a soup on the wall and remembers Hee Sung made a similar soup. The chef meets with them. He confirms Mr. Nam and Hyun Soo worked for him in the kitchen 3 years prior. Ji Won asks for contact info for Hyun Soo. The chef admits he paid Hyun Soo in cash because he didn't have a legal idea. The chef explains Mr. Nam paid him for recipes so he could open his own eatery. Hyun Soo disappeared without saying goodbye. Hyun Soo wasn't a natural with people. Ji Won remembers Moo Jin statement that Hyun Soo has a revenge-oriented antisocial personality disorder.
Hee Sung looks at the scar on his neck, the one Mr. Nam gave him.
Flashback…On a rainy night in the woods Mr. Nam yells he needs money and wants Do Hyun Soo's money. Mr. Nam stabs Do Hyun Soo. They struggle. Hyun Soo gets the upper hand pins Mr. Nam into the ground. He gets that look. Mr. Nam begs for his life.
As Hyun Soo raises his knife to strike he imagine a man there too. That man urges him to kill. Hyun Soo fights the urge. The man urges him to kill. Hyun Soo plunges the knife into the ground next to Mr. Nam and flees. When he exits the woods and staggers onto the road, a car hits him pushing him up into the air then slammed into the ground.
The car hitting Hyun Soo was a surprise. Who was that guy with the soulless eyes?
Hee Sung gets a call from Moo Jin. He tells Hee Sung he's now his alibi for the Mr. Nam's murder. He wants to meet. Hee Sung doesn't want to see him again. Moo Jin points out Mr. Nam was a pain in the neck. He agrees and isn't sorry the man is dead. He warns Moo Jin not to bother him again. Then there's a knock on the door. Moo Jin bursts in the house. Hee Sung motions that his daughter on the couch watching TV. He shows Hee Sung the video of the murder from the news report. He says that the police suspect Hyun Soo. Eun Ha asks who Hyun Soo is. Hee Sung shoves Moo Jin outside to talk there.
Stupid of them to have a conversation in front of Eun Ha. She's a curious intelligent little girl.
Hee Sung asks why Moo Jin is there. Moo Jin asks who killed the foreman. Hee Sung says he did. Moo Jin asks who killed Mr. Nam. Hee Sung say he did not. Moo Jin observes Hee Sung may be a killer but he doesn't lie. Hee Sung slams Moo Jin against the wall and demands he cut to the chase. Moo Jin asks if Hee Sung threatened Mr. Nam. Hee Sung says he did not. Moo Jin points out Mr. Nam thought Hyun Soo was threatening him which means the killer knows Hee Sung too. Moo Jin believes the killer is out to get him. Moo Jin suggests they work together to find the killer. Hee Sung asks why he would want to do that. Moo Jin offers a win-win scenario, Hee Sung can clear his name and he'd get an exclusive story.
The man in the hooded raincoat looks at a wall covered in faces. He coughs violently and spits up blood. He takes pills. We see a fish charm on his cell phone.
Hee Sung's mother sees the new report where the missing Hyun Soo is mentioned.
The police team reviews the evidence. Hyun Soo disappeared in 2005. Mr. Nam received 10K and always feared Hyun Soo. In 2008, Hyun Soo killed the foreman, burned his house and disappeared. Hyun Soo had no friends. Detective Choi wonders how Hyun Soo is surviving without an ID. Team Lead Lee wants to know about Hyun Soo's family.
Hee Sung's father arrives home.
Hee Sung's mother slaps her son angry that his name is in the current news. Hee Sung says he's investigating the situation. His mother rails she's sorry she created his alternative ID, Hee Sung.
Hyun Soo's father reveals a secret door to a room with a hospital bed. He murmurs Hee Sung to his son lying the bed.
Two family portraits reveal that Hee Sung isn't the biological son but a substitute for the real one!
OMG!!!