On an isolated oil rig platform, Hae-jun works as the equipment manager for a small, but dedicated crew. The region of sea, called "Sector 7" represents their last hope of finding oil. After an undersea expedition goes horribly wrong, other crew members begin to turn up dead; one by one, their bodies viciously multilated. What the few survivors soon discover is a transparent underwater creature they had encountered once before. The viral monster infiltrated the ship through the drilling pipe and has been feeding on the crew to survive. Hae-jun and her colleagues frantic fight for survival begins.