If a species is horrible enough, do we have the right to kill it forever? Seventy years ago, a nightmare parasite feasted on the live flesh of warm-blooded creatures in North America: the screwworm. That is, until a young scientist named Edward F. Knipling discovered a crucial screwworm weakness and hatched a sweeping project to wipe them out. Knipling’s seemingly zany plan to spray screwworms out of planes all over the continent— with US taxpayer money— succeeded, becoming one of humanity’s biggest environmental interventions ever. Today, screwworms have been gone so long that none of us in North America even remember them. But now, they’re coming back. And they’re forcing us to ask: in an era of climate change and rapid mass extinction— should we kill off a species on purpose? Special thanks to James P. Collins, Max Scott, Amy Murillo, Daniel Griffin, Phil Kaufman, Katie Barnhill, Arthur Caplan, Ron Sandler, Yasha Rohwer, Aaron Keefe, Gwendolyn Bogard, Maria Sabate, Meredith Asbury, and Joanne Padrón Carney