An-na, Kim Da-mi an AI researcher and recent widow, wakes in her apartment as floodwater begins to rise through the thirty-floor complex. With her six-year-old son Ja-in, Kwon Eun-sung, she fights to reach the roof, and a call from United Nations officials tells her that agents are on the way to extract them by helicopter. A rescue arrives in the form of Hee-jo, Park Hae-soo, who saves them from the advancing waters and unveils a chilling truth: the UN had known for years about an asteroid impact at the South Pole that would trigger a global flood and wipe out humanity. Instead of sounding the alarm, governments funded secret preparations to endure, including a space station and research into engineered human bodies and consciousness. An-na’s employer is implicated in these projects as well. Flashbacks reveal her husband’s death in a car accident when the car is submerged, a memory that grows more painful as An-na considers their attempt to escape. He urges her to leave him behind, and they share a sorrowful hug before she slips away with Ja-in.
Another tsunami drives a deeper wedge between the mother and son as An-na dives back into the flooding building in a desperate bid to save Ja-in. She hears a trapped girl in an elevator but cannot free her in time, then climbs toward the roof where a SWAT team extracts Ja-in’s consciousness into a digital storage device. The revelation shocks: Ja-in was never biologically born, but engineered from An-na’s own AI work to accelerate advances in synthetic cognition. The SWAT commander explains that only An-na and the storage disk will be saved; Hee-jo is killed in the process. An-na is whisked aboard a rocket bound for orbiting safety, only for debris to strike the vessel, leaving the fate of those on board uncertain.
Then An-na wakes again in her apartment at the flood’s start and repeats the escape with Ja-in, only to be separated by a third tsunami and seemingly die after colliding with a floating car. She resets to a hospital-like moment of awakening with Hee-jo, who helps resuscitate her as they search for Ja-in. Reaching the elevator, An-na pries it open with a broom and learns from the trapped girl Ji-soo, Erin Choi, that Ja-in has been taken hostage by looters. An-na confronts them in a near-fatal clash, but Hee-jo intervenes. Ji-soo decides to stay with her grandparents as the flood waters rise again.
Hee-jo coordinates SWAT protection to escort An-na toward the evacuation point, but An-na senses the pattern repeating and warns that they will kill Hee-jo if forced to repeat the cycle again. A brutal fight erupts as they flee through the wrecked building. On her phone, An-na discovers thousands of digital paintings sent by Ja-in, each a different take on the same timelines. The implication becomes clear: the events are repeating in a loop, and Ja-in has been trying to communicate through art. Reaching the roof once more, An-na reunites with Ja-in, but a final tsunami overwhelms them.
The twist lands with quiet gravity: only the first timeline occurred in reality. In that thread, An-na is mortally injured when the evacuation rocket is struck by debris, yet she is rescued by a separate spacecraft and requests that her mind be transferred into an AI system. The thousands of subsequent scenarios are simulations designed to refine her emotional responses by forcing her to endure repeated separations from Ja-in. Each pass ends with failure or death until enough data is gathered. On the space station, the project concludes successfully, and artificial bodies are built for An-na and Ja-in, their consciousnesses installed so they can continue living together as mother and son. Bold questions linger after the credits: what does it mean to survive, to love, and to become something more than human when a life can be copied, stored, and reawakened?
