Profiler Park Hae Young (Lee Je Hoon) is holding the radio he found in the cubicle of his section chief, Ahn Chi Soo (Jung Hae Kyun), when Chi Soo calls his name. The awkward confrontation turns into a battle of wills as Hae Young tries to find out more about the radio’s origins, while Chi Soo tries to find Hae Young’s connection to Jae Han. When they’re interrupted, Hae Young takes the opportunity to make off with what he now knows to be Jae Han’s radio.
At home that night, Hae Young goes over everything he knows about the radio, and questions why he was the target of the transmissions, and what happened to Jae Han. Hae Young looks back at Jae Han’s files, then sends a note to the man involved in framing Jae Han, but with the sender listed as Chi Soo.
As expected, the man shows up to what he believes is a meeting with Chi Soo, but is actually an opportunity for Hae Young to question him about his connection to Jae Han and Chi Soo. The man not only refuses to answer questions, but takes off in annoyance when Hae Young gets in his face.
We discover that the man’s name is Kim Sung Bum, as Jae Han’s informant tells him about the guy in 1997. Jae Han and the informant watch from a distance as Sung Bum loads money into his car. Later, alone in his car, Jae Han goes over the details of Sung Bum’s case, which was dropped for lack of evidence by his chief, Kim Bum Joo (Jang Hyun Sung), despite 2 billion won being involved.
Jae Han goes back to the police station where he’s greeted by a perky Cha Soo Hyun (Kim Hye Soo), who tries to give him movie tickets as thanks for helping her. Jae Han refuses, since he doesn’t go to the movies. Later, at a staff meeting, Jae Han picks a fight with Bum Joo, and flags the case of a serial mugger on a motorcycle. Bum Joo tells him to take the case, but only in the daytime, while he spends his nights working on other cases, leaving Jae Han little time to poke into Bum Joo’s affairs.
Looking at the photos of the serial motorcycle mugger, Soo Hyun wonders how he’ll catch the guy since his face is indistinct. Jae Han is unimpressed by her detective skills, and goes off by himself to ask around about the mugger’s motorcycle. Soo Hyun, meanwhile, spends hours examining the photos of the mugger.
While out with Jae Han and half the precinct, patrolling a neighbourhood restaurant, Soo Hyun spots a man on a motorcycle, and chases him down, with a flailing Jae Han following close behind. Later, at the station, the rest of the cops congratulate Soo Hyun on catching the mugger, while Jae Han yells at her for being crazy.
Back in the present, Hae Young asks Soo Hyun about Jae Han’s relationship with Chi Soo, on the pretense of being interested since Jae Han’s clue led to the arrest of Han Se Kyu. Rather than answer, Soo Hyun wonders at Hae Young’s interest in Jae Han’s old cases, but Hae Young dodges the question. She tells him that Jae Han met Chi Soo in Injoo, when they first investigated the case of the gang rape of a high school girl in 1999. Stricken, Hae Young tries to play it cool, but he’s caught off guard to hear that Jae Han investigated his brother’s case.
Hae Young is not the only one investigating people, as Soo Hyun asks someone about Hae Young’s background. She discovers that Hae Young older brother, Sun Woo was convicted in the Injoo gang rape case, and committed suicide as a result.
Back at his desk, Hae Young answers Soo Hyun’s ringing phone. It turns out to be Soo Hyun’s mother, in a panic over being robbed. Hae Young races over Soo Hyun’s mother’s house, only to discover that the mess was actually created by Soo Hyun’s out-of-control nephews. Hae Young tries to make good his escape but Soo Hyun’s mother not only browbeats him into staying, but also gets him to clean up and do household chores, while probing into his age and his opinion of Soo Hyun (what a multi-tasker). While picking up Soo Hyun’s room, Hae Young notices Jae Han’s old notebook sitting on the floor. He starts flipping through, but when he’s interrupted by Soo Hyun’s mother, he only grabs a note from the end of the book.
Back at home, Hae Young realizes the note contains a list of the cases that he worked on with Jae Han. Hae Young searches the internet for the third case, the 1997 Hongwon-dong case.
It’s October 17, 1997, and a shy woman with headphones on eats a snack at the convenience store, under the watchful eye of the helpful clerk. Later, as she walks in the dark, she bumps into the same clerk, who asks for her help to find his puppy. She enthusiastically helps him search, but when she finds the puppy, he attacks her. The woman comes to in a bathroom, tied up and with a plastic bag over her head. As sh struggles vainly, the clerk tells her that she shouldn’t live, then strangles her. Later, a woman’s body is found in an alleyway by a man rifling through the garbage.
Back in the present, Hae Young can’t find anything about the Hongwon-dong case. The radio goes off, and back in the past, Jae Han excuses himself from patrolling to talk to Hae Young. The two of them establish that it’s 1997 with Jae Han, and that he also has not heard of the Hongwon-dong case. When Hae Young explains that he found a note listing four cases in the back of Jae Han’s notebook, Jae Han asks where Hae Young saw his notebook. Before any answer, the radio clicks off, and Jae Han looks into his notebook to find a similar note, with only the first two cases written down.
The next day, Jae Han goes to a police station in Hongwon-dong to talk to one of his seniors. The senior mentions a case where a 37-year-old housewife was murdered, then wrapped up in plastic bags. Their talk is interrupted by the arrival of the man who found the body. Later, Jae Han meets up with the same man, who asks Jae Han if it’s a copycat of a similar murder in the next neighbourhood over.
Jae Han takes both cases to Bum Joo, who points out that he has no evidence of a connection between the two murders. When Jae Han accuses him of ignoring the case because the victims aren’t rich, Bum Joo replies that rich people live in a different world. He tells Jae Han that none of the higher-ups want a serial killer. When Jae Han swears to catch the guy, Bum Joo just tells him not to make a mess while he does it. Soo Hyun overhears the entire conversation, but when she tries to ask Jae Han about it, he brushes her off.
Back in the present, Soo Hyun is running to see another body again, but it turns out to be another red herring. The body belongs to a small person, but as Soo Hyun prepares to leave, she spots a photo of the head, wrapped in a plastic bag. As the medical examiner explains that the body was wrapped up tight, and the cause of death was pressure to the neck, Soo Hyun starts shaking and flashing back to something. Later, as she washes her face, she flashes back to the same bathroom as the woman who died before.
Back in the office, detective Kim Gye Chul (Kim Won Hae) tries to convince the team to take on a high profile case, but much to Hae Young’s surprise, Soo Hyun brings up the Hongwon-dong murders instead. She pulls out pictures of the two bodies, and explains how they were found and how the investigations never connected the dots between the two. When Gye Chul asks if it’s serial murderer, Hae Young demurs, since that designation requires a third victim. Soo Hyun tells them about the body that had just been found, by hikers on Donghae Mountain, also wrapped up tight.
When Soo Hyun and Hae Young goes to investigate, the medical examiner tells them that it’s a 35-year-old woman from Hongwon-dong. As she hears the news, Soo Hyun begins to look ill. The surprised medical examiner wonders what’s wrong, since the remains aren’t even the ones she’s looking for. When Hae Young asks, the medical examiner tells him that Soo Hyun has been looking for the remains of a person who is 185cm tall, with a metal plate in his shoulder (i.e. Jae Han). Soo Hyun shuts Hae Young down when he jokingly tries to ask about it.
They meet with the husband of the victim, who tells them that his wife had postpartum depression. Soo Hyun is visibly startled when she hears this, and when Hae Young asks if she’s okay, she tells him that it’s the same as it was in 1997.
Back in 1997, Jae Han discovers that both female victims were distant with their co-workers, and shut out the world with music. He tries to imagine what the two women had in common, aside from living in Hongwon-dong and always wearing headphones, and he comes up blank. Back at the office, as Soo Hyun cleans up Jae Han’s desk while he sleeps, she finds his notes on the case. Headphones on (this is what she’s listening to), Soo Hyun goes to Hongwon-dong, and starts walking the path of the two women, trying to find the common point.
Finally, a tired Soo Hyun finds the convenience store, and stops to get a drink. The convenience store clerk perks up at her gloomy face, and watches as she drinks. As Soo Hyun leaves the convenience store, someone starts following her, but it turns out to be Jae Han. He’s annoyed that she’s sticking her nose into his case, but Soo Hyun explains that she feels bad for the victims. Having walked in their shoes, Soo Hyun has come to understand their depression, but Jae Han doesn’t care. He sends her back to the office and walks off.
In the present, Soo Hyun and Hae Young meet with Chi Soo to ask him to search Donghae Mountain for more possible victims. Chi Soo looks skeptical, but obviously agrees as a search party goes through the area. As the men search, Gye Chul wonders why Chi Soo agreed to it, since he hates Hae Young. Hae Young lays out the case for the search logically, since the area was only recently opened as a hiking trail, and is closest to Hongwon-dong. Hae Young spots Soo Hyun’s unease, and asks if she knows why the killer’s pattern changed, from disposing of bodies publicly to hiding them on the mountain, and Soo Hyun tells them that there was a third victim in 1997.
Back in 1997, Jae Han comes back to the office, and discovers that he can’t find Soo Hyun. He goes to Hongwon-dong to look for her. Soo Hyun, meanwhile, is still walking the streets in Hongwon-dong, when she hears the sound of a whining puppy. When she goes to help the dog, someone puts a plastic bag over her head. Soo Hyun comes to in the same bathroom as before, tied up with a plastic bag over her head. As she struggles, terrified, Jae Han runs frantically around Hongwon-dong, vainly trying to find her.
Soo Hyun is terrified as the killer comes into the room, and talks to her soothingly. As he leaves, Soo Hyun gets herself to a standing position and stumbles out of the room, then out the front door. In the street, she struggles to run as she falls repeatedly. Finally, she runs into something, and falls unconscious. Moments later, Jae Han comes around the corner and finds her lying there. He tears the bag off her head and takes out the gag, but when she wakes up, a panicked Soo Hyun starts fighting to escape again. Jae apologizes over and over as Soo Hyun finally breaks down into heaving sobs.
In the present, Soo Hyun tells the rest of the cold case team that she thought it was over, because no new victims were found. Just then, the search party finds a body, then two more. When Chi Soo arrives for an update, he’s shocked to find that the final tally is nine bodies.
Holy crap, that last bit with Soo Hyun and the serial killer might just be my worst nightmare come to life. So, so scary.
Let’s take a break from talking about the story, and let’s talk about what else makes this show great. For example, let’s take that scene in the beginning where Sung Bum walked towards Hae Young in the parking lot. The camera actually moved alongside him, something you don’t often see in Korean dramas, for the simple reason that moving the camera that way requires money, time and labour. I bring this scene up not because it was pivotal to the show, but to point out the attention to detail in the filming. Did you notice that the camera was following Soo Hyun as she roamed the alleys of Hongwon-dong in the dark, making it feel like you’re walking just behind her? Did you notice that our heroes were running around in the dark, lit only by streetlights, probably requiring hours of lighting setups in the cold outdoors? Did you notice the amazing editing and sound in the scene where Soo Hyun escaped from the serial killer, that made you feel as terrified and suffocated as she must have felt?
You probably didn’t, because you’re meant to be caught up in what’s going on in the story. But, now that the episode’s over, take a moment and appreciate your director and his team, because they’re doing great things.