From international bestselling sensation Thomas Olde Heuvelt comes Echo, a thrilling descent into madness and obsession as one man confronts nature—and something even more ancient and evil answers back.“A compulsive page-turner mixing supernatural survival horror and adventure.” —Paul Tremblay, author of A Head Full of Ghosts and The Pallbearers' ClubNature is calling—but they shouldn't have answered.Travel journalist and mountaineer Nick Grevers awakes from a coma to find th