A year after losing his friend in a tragic 4,000-foot fall, former ranger Gabe Walker and his partner, Hal, are called to return to the same peak to rescue a group of stranded climbers, only to learn the climbers are actually thieving hijackers who are looking for boxes full of money.
Distraught, confused, and half-wild with fear, Sarah Carter emerges alone from the Appalachian cave system where she encountered unspeakable terrors. Unable to plausibly explain to the authorities what happened - or why she's covered in her friends' blood - Sarah is forced back to the subterranean depths to help locate her five missing companions.
When Travis, the mouthy son of a criminal, disappears in the Amazon in search of a treasured artifact, his father sends in Beck, who becomes Travis's rival for the affections of Mariana, a mysterious Brazilian woman. With his steely disposition, Beck is a man of few words -- but it takes him all the discipline he can muster to work with Travis to nab a tyrant who's after the same treasure.