On a sweltering summer night in the rundown town of Niagara Falls, New York, the power flickers and goes out. Within 48 hours, the blackout has cascaded across North America. For Jimmy Ledanski, reluctant manager of a tourist-trap motel, wounded and reeling from a recent suicide attempt, the outage at first barely registers. For his friend Anna Eisenberg, trapped in Maine at a nursing conference, the minor inconvenience rapidly spirals into a struggle...