1920s Oklahoma. The richest people per capita in the world were members of the Osage Indian nation in Oklahoma after oil was discovered beneath their land. Then, one by one, the Osage began to be killed off. The family of an Osage woman, Mollie Burkhart, became a prime target. Her relatives were shot and poisoned. Many of those who dared to investigate the killings were themselves murdered. It became the FBI's first major homicide investigation ... and the bureau badly bungled the case. J. Edgar Hoover turned to a former Texas Ranger named Tom White, who put together an undercover team which began to expose one of the most chilling conspiracies in American history.