Agent Michael Walker returns when multiple deaths at Glacier Bay National Park are just the first steps in a potential global disaster.

National Park Service investigator Michael Walker is battling smugglers stealing priceless artifacts when he’s dispatched to Glacier Bay National Park in Alaska, where, in the first stage of a potential global disaster, a team of scientists has gone missing.

Meanwhile, in Florida’s Everglades National Park, FBI special investigator Gina Delgado traces the murder of an environmental science intern back to another U.S. Geological Survey team’s ongoing experiments that are decimating the fragile ecosystem. That is before she’s dispatched to the scene of a sunken U.S. nuclear submarine, the entire crew of which has inexplicably been killed.

The connection between these disparate investigations lies in a deadly prehistoric organism, frozen for thousands of years in the ice until global warming brings it back to life in what could mean the death of all life on Earth. An organism that a rogue billionaire sees as the ultimate fuel source and a Russian strongman views as the ultimate weapon that can shift the global balance of power forever. Against that backdrop, Walker and Delgado find themselves desperately doing battle across multiple fronts against an ancient, unstoppable enemy.