An experimental military sonar tests trigger the release of two massive prehistoric creatures: a colossal shark and a gigantic octopus, both encased in ice for millions of years. Marine biologist Emma MacNeil witnesses strange behavior in marine life and soon discovers the existence of these two ancient monsters. As the shark attacks a passenger plane and the octopus brings down an oil rig, chaos ensues across the globe. Emma collaborates with her former professor, Lamar Sanders, and Japanese scientist Dr. Seiji Shimada to find a way to contain or destroy the creatures.

While the trio races against time to come up with a solution, they face bureaucratic hurdles and militaristic interventions as governments worldwide panic and take extreme measures. The team develops an audacious plan to lure the shark and octopus into a confrontation, hoping the ensuing battle will result in mutual destruction. Just as they set their plan into motion, unforeseen variables threaten to derail their efforts, leaving humanity's fate hanging in the balance.