Netflix isn’t just sticking to one suspense-filled film this holiday season with Wake Up Dead Man; they’ve also unleashed a deluge of excitement with the South Korean disaster flick, The Great Flood. Directed by Kim Byung-woo, this sci-fi thriller has rapidly climbed into Netflix’s Top 10 movies chart as 2025 comes to a close. If you’ve found yourself captivated by the apocalyptic flood imagery featured on the platform, you’re not alone.

Curious about the film’s conclusion? More importantly, what does it signify when An-na races against time and technology to save both humanity and her son, Ja-in? When the storm clouds gather, DECIDER is here to guide you through the chaos.

The Great Flood plot summary

The story begins like any other day. An-na (played by Kim Da-mi), a weary single mother and researcher, wakes up next to her energetic young son, Ja-in (Kwon Eun-sung). He’s eager to dive into swimming and adventures, but she’d prefer to start her morning in a more laid-back manner, scrolling through her phone. Ja-in, however, astutely notices her screen addiction.

The day quickly takes a dramatic turn as a heavy downpour escalates into a severe flood. The rising waters soon flood An-na’s apartment, threatening to destroy her entire complex. As An-na carries Ja-in to safety, the building succumbs to the relentless waves, and she witnesses other people being swept away by the current.

Amid the chaos, An-na encounters Hee-jo (played by Park Hae-soo), who provides vital information: an asteroid has collided with Antarctica, causing sea levels to rise drastically. Japan has already been submerged, and Korea is next in line. Hee-jo entrusts An-na with a critical mission. As the last surviving researcher from the Darwin Center, she is tasked with completing the Emotion Engine—an AI project intended to reconstruct humanity after a potential extinction event on Earth.

As the waters continue to rise, soldiers evacuate An-na to a spacecraft to leave the planet – and Ja-in, whose head is getting shaved and potentially sliced open by some other armed men as she leaves. Out in the cosmos, the grand design of The Great Flood begins to snap into place through flashbacks of previous conversations with the center’s leadership. All the other researchers have managed to snap into place the necessary components to regenerate humanity through AI, but An-na and her colleague still struggle with the emotional component.

An-na posits there is no stronger feeling than the bond between mother and child, which would mean the clearest sign that the Emotion Engine works is if someone put aside all instincts for self-preservation if it meant self-sacrifice for one’s offspring. Thus, she volunteers herself to be sprung into a maze-like scenario to test out the hypothesis. In a Groundhog Day-esque experience, a synthetic version of An-na continues reliving the flood day after day until she can prove herself capable of exhibiting that deepest of human emotions.

An-na believes that if she can be conditioned to put her son above herself, then the Emotion Engine will be ready to recreate humanity. Each time, she’ll have no concrete memory of her previous runs through the scenario, just the emotional muscle memory of how one should act when faced with an extinction-level event. She’s simultaneously the power behind the engine and its guinea pig to become the ultimate proof of concept.

And after thousands and thousands of simulations, enumerated each time by the number on her shirt, An-na begins to get the hang of the whole mothering thing. She makes it progressively further through the fake flood by coming to help others along the way. Another young girl stuck in an elevator, an elderly couple struggling through the disaster, and a pregnant woman going into labor at the worst possible time all find themselves beneficiaries of An-na’s burgeoning sense of service.

The Great Flood ending explained

Eventually, An-na comes to a point in the simulated floods where she must ultimately decide not only her own fate but that of Ja-in. That final moment on earth when she leaves him with the guards becomes the key juncture. If she can summon the strength to prioritize this one life over her work to save humanity, then An-na will have proven her own thesis. After synthesizing all she’s learned, including fighting off the militarized security inside the complex, An-na reaches this moment where she can finally achieve her vision.

But as An-na lurches for Ja-in, breaking free of the soldiers trying to escort her to space, a series of flashbacks and fragmented memories begin to cast An-na’s breakthrough in a new light. Five years before the first/real flood, she met with her boss Hyen-mo (Jeon Hye-jin) with doubts that her Emotion Engine could deliver the necessary outcome. Hyen-mo disputes An-na’s assertion that experiences can deliver emotions, especially when she needs results at a time when the fate of the species hangs in the balance.

An-na reluctantly agrees to an altered experiment design where she will take care of a synthetic child and see if she can summon up the maternal instinct for it. This kid in her care is … Ja-in. In montage, The Great Flood takes viewers through An-na’s first five years of motherhood – and explains a key reason for her trepidation around the water through her husband’s drowning in a car accident.

Depending on how one wants to look at it, the climax of The Great Flood represents An-na beating the engine’s simulation of reality or fulfilling its mission. She’s able to throw off her security detail and bring Ja-in into the Emotion Engine with her, thus proving that it is possible to generate emotion through experiences. Now, alongside logic and intelligence, the AI humanoids are ready to repopulate.

An-na and Ja-in then head back to earth together in a spaceship to begin this mission, but there’s one plot point raised by the ending of The Great Flood that cannot be so easily explained. Is this version of An-na the woman herself, with all the memories and experience she’s gained from participating in the simulated floods? Or is it an AI-generated version of her that’s merely been trained on the experiences she gave to the engine? Did she save humanity or hasten their obsolescence? There’s evidence for both, although the fact that An-na works for the Darwin Center certainly invites viewers to think about the film in the context of natural selection.

It’s a lingering question mark, and perhaps one that explains why The Great Flood has such a resonance in the year when TIME Magazine named AI architects their person of the year. It remains unclear if all this technology being developed with lifelike, humanistic functionality is ultimately going to accentuate life or supplant it altogether.

Marshall Shaffer is a New York-based freelance film journalist. In addition to Decider, his work has also appeared on Slashfilm, Slant, The Playlist and many other outlets. Some day soon, everyone will realize how right he is about Spring Breakers.