The Obsidian Chamber by Douglas Preston
A TRAGIC DISAPPEARANCE. After a harrowing, otherworldly confrontation on the shores of Exmouth, Massachussetts, Special Agent A.X.L. Pendergast is missing, presumed dead. A SHOCKING RETURN Sick with grief, Pendergast's ward, Constance, retreats to her chambers beneath the family mansion at 891 Riverside Drive - only to be taken captive by a shadowy figure from the past. AN INTERNATIONAL MANHUNT Proctor, Pendergast's longtime bodyguard, springs to action, pursuing Constance's kidnapper through cities, across oceans, and into wastelands unknown. BUT IN THIS WORLD, NOTHING IS AS IT SEEMS And by the time Proctor discovers the truth, a terrifying mechanism has stirred - and it may already be too late...