A small fissure has opened in the bedrock under Manhattan, and miles beneath the surface of the earth an awesome natural time bomb is ready to spew steam, boiling-hot sediment, and molten rock down every street and avenue of the city.

There is one person in New York who knows what is happening – Janet McCoy, a beautiful and brilliant young geologist specializing in volcanic activity. She believes that recent subway excavations in Central Park have unearthed more than a few steam pipes. She has found, among the blasted stones at the site, one crucial and terrifying clue – a fragment of “Genesis rock,” part of the earth’s inner crust that surfaces only through the violence of volcanic eruption.

If she’s right, New York has only hours to prepare for the most horrifying natural disaster in modern history. Janet McCoy knows there may be time to evacuate, or even contain the eruption – if she can only find someone who believes her.

So she telephones the President of the United States…