Last Island — Louis Tridico

Four elaborate mausoleums are found deep in the Louisiana swamp, far from any town. Inside are 21 bodies, yet there are no markings, no names, no dates. Historian Emma Eaton is asked to investigate. What she discovers leads to a mystery that began during a violent hurricane in 1856, with connections to a crazed itinerant preacher and a centuries-old feud between two prominent families. But there are forces at work to stop her. One, a reclusive Native American who wants the tombs left alone. The other, the massive floodwaters of the Mississippi River, threatening to destroy a dam and wash away the answers. Either could bury Emma once and for all, and forever hide the secrets of Last Island.