Heaven's Keep: A Novel (Cork O'Connor #3) by William Kent Krueger; 2010. Softcover.

Intrepid hero Cork O’Connor faces the most harrowing mission of his life when a charter plane carrying his wife, Jo, goes missing in a snowstorm over the Wyoming Rockies. Months after the tragedy, two women show up on Cork’s doorstep with evidence that the pilot of Jo’s plane was not the man he claimed to be. It may not be definitive proof, but it’s a ray of light in the darkness. Agreeing to investigate, Cork travels to Wyoming, where he battles the interference of local law enforcement who may be on the take, the open hostility of the Northern Arapaho, who have much to lose if the truth is known, and the continuing attempts on his life by assassins who shadow his every move. At the center of all the danger and deception lies the possibility that Jo’s disappearance was not the end of her, that somewhere along the labyrinthine path of his search, maybe even in the broad shadow of Heaven’s Keep itself, Cork will find her alive and waiting for him.