THE NIGHTMARE DOESN'T END. IT BEGINS AGAIN.

Seawater is pouring into the North Pacific International Undersea Station. Sabotaged by a fanatical cult, the base is flooding fast and crawling with armed men as the crushing pressure outside begins to force its way in.

Trapped far beneath the surface, Muhyeon and a small group of Korean survivors are driven into a brutal race through a maze of destruction, where every wrong turn feels like it could be their last. Thrown into a world where hesitation means death, Muhyeon feels his grip on reality slipping with every step.

When the chaos culminates in a shocking tragedy no one could have foreseen, the base's inhabitants find themselves in much greater peril—and time is not on their side.