Soo-Young, a man who lost his dreams after a tragic accident, boards a luxury cruise with his younger sister, Hee-Soo, hoping for one last chance at peace. But the voyage quickly turns into a nightmare. A mysterious virus outbreak spreads through the ship, and terrifying monsters that steal human heads begin their hunt. In the chaos, Soo-Young is separated from his sister. Now trapped on an isolated cruise in the middle of the ocean, with nowhere to run but the endless sea, he must fight to survive and find Hee-Soo before it’s too late.