In March 1925 a tornado whipped across the Midwest, leaving hundreds dead. But as Ms. Southwood writes in this elegiac first novel, the storm’s work was not yet done. She focuses on the Graveses, the only family in the devastated town of Marah that was spared any loss, and shows the destructive force of their survivors’ guilt. “Standing there in the yard, they’d been like figures glued inside a snow globe with the remains of their neighbors’ shredded possessions drifting down around them,” Ms. Southwood writes. Although she dwells a little heavily on the townspeople’s resentment, subtlety usually prevails. Paul Graves worries about cleaning up the debris in his yard, fearing that the neighbors will see it as preening. The family starts staying inside more, and Paul’s wife, Mae, retreats further into herself. Having everything turns out to be too much.