Sinking thousands of feet below the surface of the earth in the Leister Deep copper mine in Minnesota, Philip Mercer rides a series of heavy-duty elevators to visit his old friend and mentor, Abraham Jacobs. Jacobs has led a research team to the deepest section of the mine for a groundbreaking study into climate change and cosmic rays. But as Mercer approaches the bottom, he is stunned to hear the unmistakable report of automatic gunfire in the massive underground chambers. He can't stop the inevitable: by the time Mercer finds his way to them, his dear friend, and the entire research team, have been efficiently executed. Mercer is left seeking answers...and revenge. This sets in motion a propulsive thriller intertwined with intrigue, vengeance, and cutting-edge science. Mercer is thrust into an international hunt for the murderers--and the frightening secret of what they were looking for.