A humiliated and guilt-ridden Soo-yeol is washing his face in the washroom when he receives a call. It’s Kyung-tae calling from a payphone — he’s regained consciousness, but he’s being chased.
We rewind to two hours before In-bum’s death. Standing over an unconscious Kyung-tae, In-bum had filled a syringe with a suspicious liquid. As In-bum draws near to inject it into the IV drip, Kyung-tae’s fist clenches slightly. He’s awake, but he can’t show it.
Luckily, he’s saved in the nick of time by the police officers who have returned from their break. In-bum takes his frustration out on them, and by the time he turns around, Kyung-tae has disappeared. In-bum notices the open window and rushes out of the room, only for the cabinet door to creak open after he’s gone. Smart cookie Kyung-tae had hidden inside.
After searching the surroundings to no avail, In-bum gets into his car to give chase, only for Kyung-tae to accost him from the backseat. Holding a scalpel to In-bum’s neck, Kyung-tae demands to know if he killed Yoo-na.
In-bum denies it, then reveals that the murderer is Assemblyman Do. Kyung-tae doesn’t believe him, so In-bum retrieves a duffel bag from his gym and hands over a voice recorder to Kyung-tae. In-bum had recorded Assemblyman Do’s assault on him.
When In-bum scoffs that someone like Kyung-tae won’t be able to take Assemblyman Do down, a determined Kyung-tae counters that he will, then escapes from the car with the duffel bag.
Back in the present, Kyung-tae tells Soo-yeol that he knows who killed Yoo-na, and entreats him to help catch the culprit.
Before Soo-yeol can leave the washroom, Assemblyman Do comes sauntering in. He dismisses Soo-yeol, who insists that he’ll wait to see him off. With a smarmy chuckle, Assemblyman Do reminds Soo-yeol that Kyung-tae’s waiting for him, isn’t he? Oh no…
Later, Assemblyman Do gets into the drug dealers’ car. They inform him that they’ve taken care of In-bum and recorded the deed on a phone. However, they went through In-bum’s dashcam footage and saw him handing over the voice recorder to Kyung-tae. Incensed, Assemblyman Do orders them to bring Kyung-tae to him.
Hee-gyeom seeks Gye-shik out to ask him about the deceased Min-soo. Informing him that Min-soo had been pursuing Assemblyman Do, Hee-gyeom theorizes that Shim Sang-ho, the drug dealer that killed Min-soo, may have done so under the assemblyman’s orders.
Meanwhile, Soo-yeol meets up with Kyung-tae in an empty, deserted office. In a resigned tone, Soo-yeol tells Kyung-tae that there’s nothing they can do without evidence or witnesses. Kyung-tae offers In-bum’s recording, but Soo-yeol’s quick to shut it down. Nowhere in the recording does Assemblyman Do explicitly admit that he murdered Yoo-na. With everything being circumstantial, they have no proof, especially now that In-bum is dead.
Chastened, Kyung-tae apologizes for troubling Soo-yeol, then thanks him for helping him — Soo-yeol was the only person he could think of. Soo-yeol exasperatedly reminds Kyung-tae that he’s being framed for murder; he ought to be worrying about himself, not others. Kyung-tae apologizes again, and Soo-yeol sighs that the powerless have no choice but to apologize and kneel.
Outside, Soo-yeol recalls how he sacrificed his dignity to grovel in front of Assemblyman Do. Grimly, he makes a call to the assemblyman.
Before long, Assemblyman Do’s hired drug dealers are entering Soo-yeol’s old office. Kyung-tae awakens to a whole gang of men, who step aside to let Assemblyman Do through. Following behind is a morose Soo-yeol, who can’t meet Kyung-tae’s betrayed gaze.
His eyes shining with unshed tears, Kyung-tae asks disbelievingly how Soo-yeol could do this to him. Soo-yeol informs Assemblyman Do that this place will be deserted till dawn, and Assemblyman Do orders his men to wait outside.
He tells Kyung-tae to sit down so they can talk, and when Kyung-tae doesn’t obey, he steps up onto the table to kick him down. Acting aggrieved, Assemblyman Do demands to know why Kyung-tae is making life difficult for him.
In response, Kyung-tae asks him if he killed Yoo-na, but Assemblyman Do blatantly lies that he doesn’t even know her at all. Cackling gleefully, he points out that Kyung-tae has no proof.
Soo-yeol steps forward, pushing Kyung-tae down to steal the voice recorder from him. Smugly, Assemblyman Do says that he tracked Kyung-tae down because he seemed to have no intention of giving up, so he’ll help him out.
Holding Kyung-tae in place, Assemblyman Do orders Soo-yeol to hand him one of his golf clubs. Assemblyman Do delivers a brutal beating to Kyung-tae, while Soo-yeol watches with a grimace.
Flashback: Hee-gyeom tests a mini camera, then tucks it into Soo-yeol’s blazer. Oh, thank goodness — Soo-yeol’s apparent betrayal was all part of the plan! Jae-sun voices his reservations, but Kyung-tae’s determined to see it through. All this started because of him, so he feels that he ought to resolve it.
In the present, Kyung-tae is beaten bloody and writhing in pain. Clutching at Assemblyman Do’s ankle, Kyung-tae grits out that he’ll catch him no matter what it takes, angering Assemblyman Do. Gripping Kyung-tae’s collar, he rains vicious punches down on him.
Jae-sun can’t bear to listen to the beating anymore and moves to barge in, but Hee-gyeom stops him. If they interfere now, Assemblyman Do will only be charged with assault.
Barely conscious, Kyung-tae ekes out that even if he dies, the truth that the assemblyman is a murderer will eventually be revealed. Finally losing it, Assemblyman Do stomps on Kyung-tae’s battered body, screaming that he has no idea why he killed that woman.
Soo-yeol and the team immediately snap to attention, as Assemblyman Do shrieks that he’s sure he killed Yoo-na because she deserved to die. Furious and fully intending to murder Kyung-tae too, he winds up for a punch, only to be kicked aside by Soo-yeol.
Soo-yeol shouts that it’s over for Assemblyman Do, then rushes to check on Kyung-tae. Hearing the commotion, the drug dealer returns and swiftly tackles Soo-yeol to the ground. He helps Assemblyman Do up, and they make a run for it. Weakly, Kyung-tae urges Soo-yeol to go chase after Assemblyman Do, and to catch him no matter what. Soo-yeol promises that he will.
Running through the streets, Soo-yeol finally catches up to Assemblyman Do, who smirks upon noticing that Soo-yeol’s alone. The drug dealer slips on brass knuckles and punches Soo-yeol until he collapses.
Assemblyman Do thinks he’s won, until Soo-yeol staggers to his feet. Yelling that the place reeks of a garbage stench because of Assemblyman Do, Soo-yeol’s face flickers back and forth until we see K in his place.
K makes quick work of the drug dealer, then chases Assemblyman Do until they arrive at a dead end. Before K can do anything, though, Soo-yeol stops him in his tracks. He wants to take it from here — he still has a score to settle with Assemblyman Do for how he humiliated him.
Striding towards Assemblyman Do, Soo-yeol declares that he’s under arrest for the murder of Jung Yoo-na and the assault of Officer Oh Kyung-tae. He tells Assemblyman Do that the person who kicked him in the face genuinely wasn’t him, but this time? It’s him.
With that, Soo-yeol punches Assemblyman Do square in the face, sending him flying to the ground. Watching from behind, the corner of K’s lips quirk up in a small, proud smile.
Backup arrives, and Kyung-tae’s wheeled into an ambulance on a stretcher amidst Soo-yeol’s worried hovering. Hee-gyeom notes that Soo-yeol has changed lately, so Jae-sun nudges her to get back together with Soo-yeol. That earns himself a headlock, ha.
The next day, the news is reporting on Assemblyman Do’s crimes. Recuperating from his injuries, Kyung-tae gives an interview in the hospital, which In-sun sees on the television. Aw, he’s wearing her clover bracelet, and In-sun lights up upon noticing it.
Some time later, Soo-yeol pays In-sun a visit. Kyung-tae’s there too, and the two wave excitedly upon noticing Soo-yeol. Along with Jae-sun and Yoo-na’s brother, they set up a barbecue lunch on the rooftop. In-sun happily feeds wraps to Kyung-tae and Soo-yeol, and it’s the cutest thing ever.
Indoors, Soo-yeol shows In-sun the video message that her mother had left for her. He closes the door to give her privacy, and In-sun cries as she hears her mother’s final words to her.
Gye-shik has been reinstated, to the elation of the narcotics team. They quickly get to work — a premium-grade drug known as ‘Pupil’ was found in Assemblyman Do’s possession. In recent years, the drug cartel’s influence in their district has grown rapidly, but the police still don’t have much information on them.
They suspect that Min-soo was murdered by the drug cartel, but the team maknae Kyung-joon tentatively points out that Sang-ho handled low-quality drugs, unlike those that the cartel deals with.
In his office, Bong-pil praises Soo-yeol for his accomplishments. Soo-yeol asks about his alleged bribery case, and to his surprise, Bong-pil informs him that the prosecution dropped the charges. A call to the prosecutor in charge reveals that Soo-yeol donated all the money in his bank accounts to a youth shelter. In despair, Soo-yeol tries to ask the youth shelter for a refund, but of course they can’t grant it.
On the rooftop, Soo-yeol demands for K to show himself, then threatens to jump off and kill them both if he doesn’t come out by the count of ten. He counts up to seven, getting increasingly flustered, before K gives him a small shove that has him screaming.
K points out that Soo-yeol ought to be grateful, since he saved him from going to jail. Soo-yeol demands to know if K has any idea how much he’s gone through to save up that money, to which K retorts that he sucked up to people like Assemblyman Do. Gaze hardening, he says that Soo-yeol still hasn’t learned his lesson.
Gye-shik and Hee-gyeom visit Assemblyman Do in prison to interrogate him about the deaths of Min-soo and Yoo-na. Assemblyman Do denies that he killed them, so Gye-shik switches tack and asks him about Pupil instead. Smirking, Assemblyman Do says that he got the drugs from Min-soo, angering Hee-gyeom.
Broke and unable to afford rent, Soo-yeol ends up moving into his mother’s apartment. K starts showing up everywhere, from Soo-yeol’s workplace to his bathtub. At his wit’s end, Soo-yeol proposes that they work out a schedule. He’ll give K four hours to himself every day, from 12am to 4am.
Soo-yeol sweetens the deal by proposing that K can beat up all the bad guys he wants at night. He even installs a camera in his watch, so that K can keep an eye on him.
Upon nightfall, though, Soo-yeol straps his watch to his car’s steering wheel and sneaks out to a club. He pressures the club owner for the names of the officers who accepted bribes from him in exchange for raid warnings, but it’s just so he can receive bribe envelopes himself.
Except the next thing we see, K has emerged and is flipping through the club’s ledger. When the club owner returns and makes a scene, K punches him in the face and throws the envelopes of money back at him.
The next morning, Soo-yeol vents to Geun-tak about how he doesn’t remember taking the ledger, yet it was somehow next to him when he woke up. He works himself up into a fit, eventually collapsing.
When he wakes, he’s hooked up to an IV drip. Geun-tak advises that he needs to get K under control, because the lack of sleep from constantly switching back and forth is having an adverse effect on his body. At this rate, either Soo-yeol’s main personality could disappear, or he could die altogether.
As Assemblyman Do walks through the prison halls, he’s suddenly targeted by two inmates. One holds him back while the other stabs him repeatedly in the gut, and all the other inmates walk past as if nothing is happening. Assemblyman Do is left to wail in pain on the ground as the prison guards belatedly run over.
That night, Soo-yeol is having trouble sleeping in his new abode. At exactly twelve, just as Soo-yeol finally drifts off, K awakes and rides out on his motorcycle.
K’s phone rings with a call, and he lights up upon seeing that Hee-gyeom’s calling. K realizes that his voice would sound different from Soo-yeol’s, so he replies via text messages, to Hee-gyeom’s confusion. Thinking that he’s Soo-yeol, she points out that he’s been acting odd lately, then asks why he’s been leaving her flower bouquets every night. K begins typing out a long and sappy message, only for Hee-gyeom to hang up in the face of his silence, LOL.
At the prison infirmary, Assemblyman Do is injured but alive. Gye-shik informs Hee-gyeom that the drug cartel was likely trying to get rid of Assemblyman Do since they no longer need him, so they might be able to get him to testify against the drug cartel if they can convince him to switch sides. To ensure Assemblyman Do’s safety, Hee-gyeom suggests they transfer him to another detention center this very night.
While on the road, the prison bus suddenly screeches to an abrupt stop; a man has jumped in front of the vehicle. Assemblyman Do begins screaming in a panic, distracting everyone from noticing the truck speeding right at them.
The impact sends the bus careening down a slope. Assemblyman Do is the first to regain his senses, only for an intruder to saw a portion of the bus window open. He jumps in and murders Assemblyman Do, then stabs maknae Kyung-joon to death right in front of Hee-gyeom.
Some time later, Hee-gyeom sits dazedly in an interrogation room. She’s the only survivor of the accident, making it necessary for the police to investigate her. Just then, she hears a commotion outside; Soo-yeol and K are arguing again. Walking up to the door, she asks if everything’s okay, snapping the two out of their fight.
She can’t see them through the one-way mirror, but K gazes longingly at her anyway (much to Soo-yeol’s irritation). Worry and consternation evident in his eyes, K tearfully promises that he’ll leave for good if Soo-yeol helps Hee-gyeom out of her predicament. That, along with the temptation of finally having K gone, is enough to sway Soo-yeol. Activating the mic, Soo-yeol vows to Hee-gyeom that he’ll save her no matter what.