Down there, beyond the deepest caves, below the crust and the mantle, there is another world. An old woman locked away in a Russian asylum has a secret - knowledge of a 500-year-old manuscript written by a long-dead alchemist that will show a passage to the mythical centre of the Earth. She knows it’s real because 50 years ago, she and a team travelled there. And only she made it back. Today, caving specialist Mike Monroe leads a crew into the world’s deepest cave in the former Soviet Union. 

The Arcadian returns to the dark ice in a reprisal of one of his first and most deadly missions. But this time the stakes couldn’t be higher. In 2008, a top-secret US submarine went missing on its test voyage off the coast of Antarctica. After years silent, its emergency beacon is suddenly activated, but strangely, the beacon is emanating from a point miles below the ice sheets of the frozen continent. The race is on.

Pompeii, present day: archaeologist Maria Monti is working at a new dig site. Like hundreds before her she is investigating the night that Vesuvius erupted, consuming the ancient city with choking ash, scalding steam, and rivers of lava. But she has just unearthed something that shouldn’t be there, something that makes her question everything she knows about the disappearances of that fateful event. Several hundred miles away Alex Hunter’s family is holidaying in southern Italy when Mount Etna begins to shake, and ash begins to blanket the countryside....

An ancient evil awakens ... Alex Hunter has been found – sullen, alone, leaving a path of destruction as he wanders across America. Only the foolish get in the way of the drifter wandering the streets late at night. Across the world, something has been released by a treasure hunter in a hidden chamber of the Basilica Cisterns in Istanbul. Something hidden there by Emperor Constantine himself, and deemed by him too horrifying and dangerous to ever be set free.

When a plane crashes into the Antarctic ice, exposing a massive cave beneath, a rescue and research team is dispatched. Twenty-four hours later, all contact is lost. Captain Alex Hunter and his highly trained squad of commandos are fast tracked to the hot zone to find out what went wrong - and to follow up the detection of a vast underground reservoir.