Suffering post-traumatic stress from her last outing (Winter Study), park ranger Anna Pigeon accompanies her husband on a white-water rafting vacation that turns into the worst river adventure since James Dickey's Deliverance. Anna and spouse find themselves dealing with the loss of the raft, the discovery of a dying pregnant woman and a sniper picking off members of the party. But it's not until they're rescued that the real trouble starts. Barbara Rosenblat's voice has an edge to it, which is a little off-putting when Anna is describing the beauty of a sunny day. But the tone comes in handy once the going gets rough: Rosenblat wrings every ounce of thrill out of the fights, near drownings, treacherous climbs, chases and emotional flareups. When the murderer goes bananas while holding a gun to a baby's head, Rosenblat hits a few notes guaranteed to raise goose bumps. A Putnam hardcover (Reviews, Feb. 23). (Apr.) Copyright 2009 Reed Business Information.