Embarking on a guided rafting trip with her husband, Paul, in Big Bend National Park on the Texas-Mexico border, Anna Pigeon is drawn into dangerous intrigue when one of their companions on the trip discovers a pregnant woman caught among tangled branches in the river.

Forest ranger Anna Pigeon accepts a temporary supervisory post at a crumbling fortress on an island seventy miles out of Key West, where she whiles away time reading the letters of her great-great-aunt who lived at the fort during the Civil War when it was a Union prison, but her solitude is rudely interrupted when a boat explodes and Anna discovers a link between the crimes of the past and the present.

Recovering from recent emotional trauma, National Park Service ranger Anna Pigeon goes to New Orleans to visit her friend, Geneva, only to become the target of a dark curse, prompting her to investigate what it has to do with a fugitive mother accused of killing her family.