Dozens of men, women, and children were turning up dead in the dark thickets and steep mountain passes of southern France. Survivors talked of a strange beast that never passed up prey and left the countryside barren. In his three years on the chase, Gustav Mackensen never gave up. But as time went on and the death toll climbed, he began to wonder whether this Beast was more than tooth and claw. What he found was far more dangerous.

One of history’s most enduring mysteries—what was the Beast of Gevaudan?