Book excerpt: In this mystery in Nevada Barr’s New York Times bestselling series, District Park Ranger Anna Pigeon is betrayed by nature itself, as a most unnatural evil stalks its prey in the pristine West… Straddling the border between Montana and Canada lies the Waterton-Glacier International Peace Park—Anna’s home away from home when she is sent on a cross-training assignment to study grizzly bears. Along with bear researcher Joan Rand and a volatile, unpredictable teenage boy, Anna hikes the back country, seeking signs of bear. But the tables are turned on their second night out, when one of the beasts comes looking for them. Daybreak finds the boy missing, a camper mutilated, and Anna caught in a grip of fear, painfully aware that her lifelong bond with nature has inexplicably snapped...