With a whale bubble gun in hand, Dae-sung (Lee Kwang-soo) confronts the “nunchucks grandpa” (Jang Won-young) at the hospital lobby, demanding to know the latter’s true identity. Moments later, “grandpa” grabs hold of Dae-sung’s girlfriend, police officer A-hee (Kim Seol-hyun of AOA), and puts a blade to her throat.
Dae-sung keeps his eyes on them as he reaches for the plastic bag “grandpa” had thrown at him, and pulls out a can of peaches – the very item he’d thrown at counterfeiter Cheon-won’s head to save his mother, Myeong-sook (Jin Hee-kyung), who was being strangled by him. Cheon-won taunts A-hee about her boyfriend – but gets caught off guard when she releases herself from his grip and throws him hard on the ground in an arm lock.
As Dae-sung confirms that “grandpa” and Cheon-won are the same person, A-hee is left in slight disbelief. To Dae-sung’s surprise, he finds out that A-hee (then an elementary school student) was an accidental witness of what happened all those years ago at the supermarket, and had thought Dae-sung killed Cheon-won.
In the midst of coaxing a confession from Cheon-won for Kwon Bo-yeon’s murder, A-hee and Dae-sung receive calls informing them about Kyung-a (Kwon So-hyun), whom Myung-sook and Seo Cheon-kyu (Ryu Yeon-seok) had discovered dead in her apartment. Dae-sung rushes over to the crime scene and manages to get to Myung-sook, who is overcome with grief and guilt over how she’d previously treated Kyung-a at the supermarket. It is then that Dae-sung tells his mother that he’d caught Cheon-won, and that the counterfeiter is the one who killed Bo-yeon and Kyung-a.
Myeong-sook is dealt with a double whammy as she sees Cheon-won being brought to the scene, and finds out that “nunchucks grandpa” was actually him all along. She berates him for his vengeful actions and the long-lasting post-traumatic effect it’s left on Dae-sung, which has left him unable to concentrate on his exams. Cheon-won, on the other hand, demands to know why he was left for dead back then when Officer Kim Doo-hyun (Kang Gil-woo) had found him in the dumpster.
Amid the hullabaloo, police detective Choi Ji-woong (Bae Myung-jin) arrives with his team and puts a stop to it, with Officer Kim tasking A-hee to send Myung-sook, Dae-sung and Cheon-kyu off. Just as they were leaving the complex, Dae-sung spots a hooded Saeng-seon (Park Ji-bin) loitering on a higher floor of the building.
Dae-sung and A-hee spend the night drinking on the supermarket rooftop, with Dae-sung using a toy laundry machine to mix up alcohol. He explains to A-hee that he’d learnt this trick from Bo-yeon, when he last encountered her at the supermarket. A-hee asks her boyfriend why he’s so obsessed with her case, and his answer was simple: “Bo-yeon and Kyung-a were both fine and alive.”
Over at the police station, Detective Choi interrogates Cheon-won, who admits to hanging the Daesung Mart bags on the women’s doors to elicit fear, in order to “get revenge” on Dae-sung and Myung-sook. To Detective Choi, Cheon-won had pretty much confessed to stalking, much to the latter’s vehement disagreement. Distressed, Cheon-won goes off on a tangent about how Dae-sung had put him in jail, how his business ended up failing and how he started to age prematurely to a point where people started calling him “grandpa”. Cheon-won even alludes to how Dae-sung might be the killer, having almost killed someone once – him.
At the supermarket the next day, Dae-sung is shocked when he hears from Gong-san (Kim Mi-hwa) – who had been at the police substation – that while Cheon-won could be charged for stalking, he wasn’t identified as the murderer. He rushes out in the middle of his lunch to talk to A-hee, who warns him to watch his back, even passing him a stun gun for Myeong-sook to keep on hand just in case. As Dae-sung also has a connection with Choco Pies and canned peaches, A-hee fears that he might be under suspicion as well, and tells him not to discuss the case with anyone else but her.
Dae-sung observes Saeng-seon (whose real name is Kang Sung-yoon) finally coming out of his shell and charming the female customers over at the fish department, but also notes some questionable body language. Upon doing a quick background check, Dae-sung finds out that Saeng-seon lives in the same apartment block as Kyung-a. While in the break room, Dae-sung goes through Saeng-seon’s locker and finds women’s cosmetics, even lingerie, in a pouch. He gets narrowly discovered by Saeng-seon himself when he goes in to get a fresh pair of rubber gloves, but manages to secretly nick his apartment key card.
Dae-sung heads to the complex and sneaks into Saeng-seon’s apartment. While rummaging through Saeng-seon’s things, Dae-sung comes across a closet full of women’s clothes, including stockings – and a cardigan that he recalled Kyung-a wearing on her last visit to the supermarket. Saeng-seon returns home early, having sold all his seafood wares, and Dae-sung makes it out of his apartment on time – by leaping out of the window. As he hangs precariously from the second-floor balcony, he sees Saeng-seon working on adding hair extensions to a long-haired woman’s wig with a glue gun, and then dolling himself up with make-up (“He’s even better than me,” admits A-hee, who had come to join Dae-sung).
That evening, Dae-sung and A-hee trail Saeng-seon – fully dressed as a female – down a shopping street, but end up losing him part way. Meanwhile, as Ya-chae (Oh Hye-won) heads home from a nearby convenience store, she quickens her steps as she senses that she’s being followed. She freaks out even more when she realises that the stalker had followed her all the way into her apartment block. The next morning, a visibly-shaken Ya-chae turns up late for work, telling her colleagues about her stalking ordeal. Dae-sung eyes a shifty Saeng-seon, while a concerned Jung-yook (Lee Kyo-yeob) – who has a crush on Ya-chae, despite her being married – offers to accompany her home, just to be safe.
Business carries on as usual until a rock comes flying through the glass window, missing an already-shaken Ya-chae by a hair’s breadth. Dae-sung heads out to find Cheon-won – who had been released by the police – with another huge rock in hand, ready to take aim. As Al-ba (Jo A-ram) calls the police, an agitated Cheon-won continues his pitiful spiel of how his life was ruined because of Dae-sung, who shoots back that Cheon-won was the one who’d hurt his mother, Myung-sook, first. They continue to trade barbs at each other even after the police arrives.
As Cheon-won is taken away, Detective Choi approaches Dae-sung and asks for his alibi on the nights that Bo-yeon and Kyung-a were killed. He adds that he has reason to believe Dae-sung could be a suspect, as his kick-scooter was found near the crime scene and his fingerprints detected on the plastic bag hanging on Bo-yeon’s door. Despite not having a warrant, the detective proceeds to search Dae-sung’s rooftop room.
When he comes across the stockings tied to his door handle, Dae-sung explains how he’d tested them out to determine which kind the killer could have used. Detective Choi’s suspicions are further aroused when Myung-sook and A-hee come storming through the door to defend Dae-sung, and decides to take him in for questioning. A frustrated Dae-sung asks the detective why he’s wasting time questioning the wrong suspect; in turn, Detective Choi points out how unsettling it is for him to seemingly know every single detail of the supermarket’s customers.
In the meantime, A-hee stakes out the police headquarters for 47 hours, before confronting Detective Choi for holding Dae-sung in custody without a warrant. Dae-sung is eventually released, with the detective warning that he’ll continue keeping an eye out. Dae-sung returns to a slightly chilly reception at the supermarket, but is warmly welcomed back by his parents frying up slices of tofu (typically given to a person released from jail, to represent a fresh start) on the rooftop. It is there that Myung-sook vows to track down the killer, so as to clear Dae-sung’s name.
Later that evening, Dae-sung, Myung-sook and A-hee gather in the rooftop room to discuss their next move, deciding to narrow down possible suspects from within the supermarket. Myung-sook and Dae-sung would keep a close watch on Gong-san (real name: Yoon Ga-hee) and Jung-yook (real name: Yang Jun-ho), while A-hee does so with Saeng-seon.
Gong-san’s criminal motive (if any) is to take advantage of fallen property prices, as it’s her dream to own a house in the neighbourhood, in her son’s name. Because of her side hustle as a door-to-door cosmetics saleswoman, she has intel on apartment statuses, thanks to her relationships with those in the maintenance offices and security posts.
Gong-san even butters up to Seo Cheon-kyu (Yul’s father), who runs his own real estate office, to get information out of him. Young-choon (Shin Sung-woo; Myung-sook’s husband and Dae-sung’s father) even lets on to Myung-sook and A-hee that Gong-san is heavily involved in the neighbourhood’s redevelopment project union, with existing rumours of her planning to buy up the murder victims’ apartments on the cheap to expand her share.
As for Jung-yook, he gets mildly irritated when Dae-sung questions him about past purchases related to the killer case (tampons and canned peaches), which turns into slight hostility when asked about his crush on the married Ya-chae. Though the trio had not followed up on Saeng-seon, it’s little Seo Yul (Ahn Se-bin) that offers up some interesting information: she had spotted him signing an apartment lease at her father’s office two months before, around the time of Bo-yeon’s murder. At the supermarket, the little girl once again picks up some other odd items, such as vegetables and a bottle of drain cleaner.
When Officer Kim stops by, he spots Dae-sung holding Bo-yeon’s pink slipper, and asks how he’d gotten it. After hearing that it was Yul who had brought it over, the officer – and eventually, Dae-sung – realises that the little girl could be an eyewitness to the case. It turns out that Yul had indeed witnessed Bo-yeon’s murder and abduction on the Catholic church grounds, and even discovered her body hidden among the thicket.
Myung-sook heads to the Seos’ residence, while Dae-sung goes to Cheon-kyu’s real estate office in search of Yul. He later returns to the supermarket to grab Saeng-seon’s key card, and rushes off. Dae-sung manages to burst his way into the apartment, but doesn’t see any trace of Yul. As he and Saeng-seon get into a struggle, Myung-sook runs in and ends up using the stun gun on Saeng-seon to knock him out temporarily. Shortly after, Dae-sung discovers Saeng-seon’s hidden room of women’s items.
When Saeng-seon comes to, he finds himself sitting on a chair with his hands tied, and the mother-son pair opposite him. Dae-sung asks about Kyung-a’s cardigan, and Saeng-seon reveals that she had given it to him before going to a friend’s house. To Saeng-seon, who identifies as female and is awaiting gender reassignment procedures, Kyung-a was her only friend, as she accepted Saeng-seon for who she is.
After Myung-sook and Dae-sung apologise to Saeng-seon, she tells them that she’d come across little Yul earlier in the day, walking the streets on her own. Little do they know that Yul was being held captive at that very moment, cowering in fear and tearfully pleading for mercy as a mysterious figure approaches her – first with stretched stockings in hand, then with a glue gun with hot glue dripping from it.
- The episode four throwback to the tender exchange between Saeng-seon and Kyung-a; for Saeng-seon, this was a memory that made losing (her) only friend even more painful.
‘The Killer’s Shopping List’ airs on tvN every Wednesday and Thursday, and is also available on Viu, Viki and iQIYI in selected regions.