The Storm Cellar on Route 9

Margaret Hensley was hanging laundry on the line behind her farmhouse outside Joplin, Missouri, when the sky turned the color of a bruise. It was May 22, 2011, and the air had gone perfectly still — that eerie, breathless quiet that every plains dweller learns to dread. She heard the sirens a full thirty seconds before she saw it: a wedge tornado, nearly a mile wide, chewing through the tree line to the southwest.…