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

In Alaska's Glacier Bay National Park, a frozen woolly mammoth is uncovered by a geological survey team. When all of them are found dead at the site of the thawed-out carcass, National Park Service ISB special agent Michael Walker is called in to investigate.

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.

Beneath the icy waters of Alaska's Elfin Cove, the crew of a stranded Los Angeles class attack submarine is wiped out by a mysterious contagion, inexplicably causing their lungs to freeze. The link between these apparently disparate events lies in a deadly, prehistoric microbe that killed the mammoth the same way it did the USGS survey team in Glacier Bay and the crew members of the submarine.

A microbe that a rogue billionaire is desperate to attain, and a Russian strongman will do anything to weaponize to achieve even greater, wide-ranging power. Fighting a battle on several fronts--militarily, intellectually, and biologically--Walker and Delgado are running out of time to stop a devastating attack that would reshape the entire world.