A geologist, his climatologist wife, two graduate students, a local newspaper reporter, an oil company representative, and a field biologist travel to one of dozens of huge holes that have mysteriously appeared in the tundra of the North Slope of Alaska. Their mission is to research these strange craters that threaten financial and environmental catastrophe should they open up under the Trans-Alaska Pipeline or any of the many oil wells and smaller pipelines that feed it. Unfortunately, a far worse danger lurks below, one that threatens to destroy all of humanity when it finally emerges. Some will live and some will die on Hell Day and the day after as the survivors flee south towards Fairbanks.