It is not yet spring in the Adirondack Mountains of upstate New York. Whitewater rafting season has already begun, however. Streams filled with snowmelt are pouring into the Hudson Gorge, an almost inaccessible twelve-mile canyon. But someone who knows every foot of the backcountry is stalking those who are attempting to run the Gorge as the river reaches flood stage.

Richard Carlyle, a former raft guide and veteran criminologist working with state and local police, is desperately searching for the person who has murdered two people already. Tracking the killer to a remote cabin in the Gorge, Carlyle confronts an ecoterrorist with a grudge against anyone who dares to invade his territory