If you thought Mousetrap had already thrown every twist it had at us, episode 9 proves there’s still plenty left in the trap. This is the episode where the show finally stops jumping between separate storylines and drags every single player, cops, gangsters, an assassin, and a man everyone thought was dead, into one mountain forest for a single, chaotic night. Here’s everything that happened, plus my honest take on whether the “everyone in one location” gamble actually paid off.
Everyone Converges on the Forest
Mousetrap Episode 9 opens with Seung-gyu and his two men, Byeong-ho and Byeong-jun, combing through the forest for the old man. Back at the police station, the Rat makes his move: he texts Moon-jae and tells him to meet up and finish this once and for all. That message is enough to pull Moon-jae away from the detectives watching him, and from that point on, he’s on the run.
Meanwhile, Seung-gyu’s group reaches a transmission tower and tries calling the assassin to figure out which direction to head. Byeong-jun quietly gets a text of his own but doesn’t say a word to Seung-gyu about who sent it, a small detail that turns out to matter a lot later. Elsewhere, the assassin has already tracked down an abandoned building and starts tearing through it, searching for the old man he’s been hired to find.
While Moon-jae is running, he literally stumbles into Seung-gyu’s crew, and a chase kicks off through the trees. Then comes the moment I genuinely didn’t see coming: a familiar face steps out of the woods. Noja is alive. A flashback fills in the gap, showing him clawing his way out of the fresh mud he’d been left in, so whatever happened before, it clearly wasn’t enough to finish him off.
Detective Park’s team also reaches the same abandoned building the assassin searched, but they come up empty-handed. Not long after, Park crosses paths with Noja himself in the forest. Noja’s only concern is finding Moon-jae and keeping him safe, but Park tries to redirect him, pointing out that Moon-jae has been lying and that the real priority should be locating the missing uncle. Noja doesn’t listen and heads off on his own path. By this point, the major crimes division has shown up too, which means there are now at least three separate groups of law enforcement plus a gangster crew and a hired killer, all converging on the same patch of forest.
Betrayal Among Seung-gyu’s Men
Byeong-ho catches up to Moon-jae first, and then does something unexpected. Instead of handing him straight to Seung-gyu, he hides him. A flashback explains why: the Rat had previously approached Byeong-ho and his brother Byeong-jun with an offer of money, dangling the idea of a fresh start away from Seung-gyu’s control.
Back in the present, Byeong-ho tells Moon-jae he plans to deliver him to the Rat alive rather than following Seung-gyu’s orders. Before he can act on it, Noja shows up and fights him, and in the struggle, Byeong-ho ends up falling on his own knife. With that threat gone, Noja turns to Moon-jae with one direct question: has he figured out who Noja really is?
The Flipped Memory: Who Actually Wrote the Rat’s Stories
While all that chaos plays out in the forest, the Rat sits down with Han Ji-hye and tells her about a man he met back in college, Seo Yu-min. This time, we get to see the memory from episode 8 replayed, but flipped completely on its head. In this version, it’s Yu-min who’s the one writing the novel, having filled entire notebooks with his own outlined stories. And it’s Moon-jae who’s in awe of the writing, not the reverse, like we were led to believe before.
The Rat drops the bombshell to Ji-hye directly: Moon-jae stole Yu-min’s work and published it under his own name. Every novel credited to Moon-jae actually belongs to Yu-min. Then he hands her the manuscript for the Rat’s second volume and instructs her to publish it exactly as written, with no edits.
Back at the abandoned building, Park notices a light on in an upstairs window and realizes someone else is inside with them.
Noja Confronts Moon-jae, and Seung-gyu Snaps
In the forest, Noja grabs Moon-jae by the throat and demands the truth about his identity. Moon-jae’s response is to pull out the text he received from the Rat, holding it up as proof that he’s the one the Rat is actually after, the “real” target, so to speak.
At the same time, Seung-gyu’s paranoia catches up with Byeong-jun. Convinced his own man is secretly working for the Rat, Seung-gyu stabs him before Byeong-jun can even react. Under pressure, Byeong-jun confesses everything, and Seung-gyu kills him anyway.
Inside the building, Park finally locates the source of that upstairs light: the assassin, hanging from one of the windows. He falls, and when Park looks outside, he spots the old man sitting alone in a corner just beyond the building.
The Forest Erupts Into an All-Out Brawl
Moon-jae, still running, crosses paths with the Major Crimes detectives this time. He and Noja take off together, eventually reaching the same building where Park and his team are stationed. Major Crimes arrives right on their heels, and when a few pointed remarks get exchanged between the rival police units, tensions boil over into an actual fight between the cops themselves.
Then things escalate even further: an entirely new group of men shows up out of nowhere, and the scene turns into a full brawl. Noja and Moon-jae use the confusion to slip away, only to run straight into another line of cops forming a perimeter around the forest.
This is where Moon-jae tries to be the hero. He offers to create a distraction so Noja can get away clean. Noja refuses the offer, instead, he hands Moon-jae the last of his cash and tells him to go be who he truly is. Then Noja runs the opposite direction, drawing the cops’ attention so Moon-jae can escape unnoticed. Honestly, this is the beat that hit me hardest in the whole episode. Sul Kyung-gu sells the moment so completely that it lands even though the show hasn’t spent a ton of time building the Noja-Moon-jae bond up to this point.
Detective Park Discovers a Family Secret
Elsewhere, Park spots the old man slipping into the forest and follows him. As he calls out, a memory surfaces, the same old man searching for him at an amusement park, years ago. It clicks: Han Hui-su is his uncle.
Before Park can process it, the assassin catches up to the old man too. Park fights him off and takes a stab wound in the process, but he manages to stop the assassin from killing his uncle by handcuffing the man to himself. Just as the assassin is about to finish the job anyway, Han-su steps in and shoots him in the head.
The Rat’s True Motive Comes Into Focus
The episode closes on the Rat, alone at a crematorium, placing a white rose near the remains of someone whose name isn’t given. He also leaves a photograph of Min-yeong there, but the listed date of death is 2022, which doesn’t line up with the woman who died in the Han River earlier in the story, since she died in the present timeline. That mismatch is deliberate, and it’s clearly setting up more to unpack later.
His internal monologue finally spells out the motive we’ve been waiting for: he wants revenge on Moon-jae for Min-yeong’s death. He also knows Moon-jae is heading to the beach where everything between them began. In the episode’s final shot, both the Rat and Moon-jae are shown making their way to Jeju Island, setting the stage for what’s coming next.
Episode 9 Review: A Bold Setting Choice That’s a Genuine Mixed Bag
Episode 9 tries something the show hasn’t really attempted before. Rather than bouncing between separate character storylines the way Mousetrap usually does, this episode funnels literally everyone, cops from two different divisions, Seung-gyu’s crew, the assassin, Noja, Moon-jae, and the old man, into one mountain forest and lets it all play out in real time. No flashback-heavy back-and-forth, no cutting between locations. Just one long night where every thread collides at once. I’ll give the show credit: it’s a genuinely different approach for this series, and there’s something satisfying about watching all these separate agendas smash into each other instead of unfolding on parallel tracks.
That said, the execution is a mixed bag. On the plus side, cramming everyone into one space does pay off in a few specific ways, it lets Seung-gyu’s betrayal of his own men play out with real tension, and the sight of rival police units brawling with each other adds a layer of chaos that feels earned given how much friction has been building between the detective teams. Those character collisions are the strongest part of the hour.
Where it stumbles is visually. Fifty minutes of forest, even with the abandoned building thrown in as a change of scenery, starts to feel monotonous by the halfway point. The show doesn’t really use the darkness or the terrain in any way that feels intentional or atmospheric, it’s just trees, more trees, and a building. The action sequences suffer for it too. Compared to the fight choreography we’ve seen in earlier episodes, nothing here feels particularly sharp or memorable.
The emotional high point, without question, is the Noja and Moon-jae goodbye. Noja sacrificing himself so Moon-jae can escape is the kind of moment that’s supposed to land like a gut punch, and honestly, it mostly does, but I think that’s more because of Sul Kyung-gu’s performance than the writing itself. The show hasn’t spent enough time deepening this specific relationship for the sacrifice to hit as hard as it clearly wants to. Sul Kyung-gu makes up the difference through sheer presence, but a stronger foundation earlier in the season would have made this scene devastating instead of just effective.
On the plot side, the Rat’s conversation with Han Ji-hye is where the real fireworks are. Getting the flipped version of the college memory, the one confirming Moon-jae stole Yu-min’s stories, recontextualizes everything we thought we understood about these two men. And tying that betrayal directly to Min-yeong’s death gives the Rat’s entire arc a sharper, more personal edge. That crematorium scene at the end, with the mismatched death date on Min-yeong’s photo, tells me we still don’t have the complete picture of what actually happened to her.
Then there’s Detective Park’s memory reveal, which honestly raises more questions than it answers. Learning that Han Hui-su is his uncle recontextualizes his entire arc, but it also leaves a lot hanging, how exactly does Park connect to Moon-jae’s story, and why do the two of them apparently share a memory from the same amusement park? And who were those unnamed men who showed up and started fighting the cops? None of that gets addressed here. With the finale on the horizon, Mousetrap has left itself a pretty tall stack of questions to answer, and I’m hoping it sticks the landing.
