Barr has honed her thriller skills to a fine point as Anna Pigeon, a park ranger on forced vacation after a traumatic case, begins a river rafting trip on the Rio Grande bordering Texas and Mexico. Accompanied by their guide, Carmen, Anna’s husband, Paul, and a small group of college students, the rafting party anticipates an exciting but not dangerous journey.

Instead, their excursion is marred by tragedy, a sniper attack, and the discovery of the body of a pregnant woman wedged into debris at the side of the raging river. Like it or not, Anna is thrust back into a professional role, she and Paul guiding the students away from danger, hunted by a killer with a powerful weapon.

The adventure turns even more bizarre when Anna realizes the pregnant woman has not yet expired, her baby still alive. She is forced to deliver the baby with nothing more than a pocket knife, the mother slipping away after murmuring, “Take my baby.” But there is little time to register the horror of the situation when the life of a newborn is at stake and a killer lurks nearby.

Oblivious to the drama unfolding on the river, ex-Secret Service agent Darden White is overseeing a formal event at a venue in Big Bend National Park by an ambitious politician, Judith Pierson, the mayor of Houston planning to announce her bid for the Governor’s Mansion. There is a long relationship between Judith and Darden, the bodyguard obsessed with protecting Judith’s interests in a rapacious political environment, where a breath of scandal can bring the most determined ambitions crashing to the ground. Darden suspects Judith has been keeping secrets from him of late, purposely avoiding his involvement in her latest scheme.

Certainly there is trouble in paradise, Judith and her husband, Charles, barely able to disguise their personal rancor from the peering eyes of observant reporters. When news of the deaths on the river reaches those at the political event, a series of confrontations result. Caught in the middle of the chaos, Anna fends off each new danger, disarmed by the tiny newborn and willing to risk death to protect the child.

Barr deftly weaves characters and plot. The stage is impressive, a vast landscape of jagged boulders and a raging river, the efforts of humans pitiful against such grandeur. Judith Pierson embodies political opportunism intruding on the beauty of the wilderness, her hubris outreaching her limitations. For her part, Anna delivers under duress, pushing personal concerns aside and experiencing an unfamiliar maternal instinct far beyond her comfort zone.

The author manipulates her characters in a macabre dance of hunter and prey, a spirited ranger confronting cold-blooded attackers. Once begun, the action never stops, a steady rain of assaults on the innocent. Barr pits the stark beauty of the wilderness against the petty schemes of man, at the same time putting human back into nature.