Grenada’s revolutionary leader was executed in a coup in 1983, with seven others. The whereabouts of their remains are unknown. Now, The Washington Post’s Martine Powers uncovers new answers about how the U.S. fits into this 40-year-old Caribbean mystery.

Lillian journeys above the Arctic Circle to one of the most remote and least visited National Parks. In our series finale, she confronts the question facing its future: whether a portion of this untouched wilderness will soon include a path for industry.

Lillian climbs the dunes for a view of a park imprinted with ancient human history and the beginnings of the Atomic Age. In doing so, she tries to understand why America’s deserts have been both safeguarded and sacrificed.