In 2006 a mysterious fungus appeared in upstate New York, killing local bats. Since then, the deadly fungus, called white-nose syndrome (WNS), has spread across the eastern United States and some Canadian provinces, killing more than six million cave bats. Pennsylvania has emerged as a major force in the national fight against WNS. This Emmy Award-winning documentary follows the efforts of scientists and government agencies to advance WNS research and save cave bats.