A catastrophic flood engulfs planet Earth, transforming cities into drowning labyrinths of steel and water. Trapped inside a high-rise apartment building slowly sinking beneath the rising tide, survivors fight against time, fear, and the crushing force of the flood. Among them are An Na and Hee Jo, two strangers bound by fate in the midst of chaos.

An Na is an AI development researcher, carrying knowledge far more valuable than she realizes. Hee Jo, a member of a human resource security team, risks everything to protect her as the building collapses around them. But as the water rises and escape routes disappear, questions begin to surface. Why is Hee Jo so determined to save An Na? And who—or what—is truly behind this desperate rescue mission?

As survival turns into a race against unseen forces, The Great Flood unfolds as a tense, emotionally charged sci-fi drama where humanity, technology, and hidden agendas collide beneath the rising waters.