Science writer Stevens describes the process of finding and identifying a treasure trove of extinct animals—full skeletons—buried in volcanic ash from an eruption in today’s Idaho. There were rhinos, horses, camels, saber-toothed deer, birds, turtles, and even bone-crushing beardogs. She recounts the ways scientists have worked together and separately since 1953 to excavate specimens, date ash layers, deduce animal behavior, figure out their environment, and identify the volcano. Poison Ivy Quarry became Ashfall Fossil Beds State Historical Park, where fossils continue to be revealed but are left in place; visitors can observe the ongoing research. Realistically, she includes some of the hiccups and dead ends. She introduces scientists, interns, and students from various fields. Her clear exposition includes examples of the clues that inform their deductions about the animals and their environment, helping readers understand how these researchers arrive at their conclusions. She explains less-familiar techniques, concepts, and equipment such as topographic maps, radioactive dating, convergent evolution, scanning electron microscopes, plate tectonics, and ground-penetrating radar. Specialized vocabulary is printed in boldface and defined both in context and in a glossary. Huynh’s brush-and-ink paintings are an inspired addition to this account of the work of re-creating a long-distant history; there are also helpful black-and-white photographs.