When Bobby McIlvaine died in the Twin Towers on September 11, 2001, his loved ones spun off in radically different directions, each mourning in his or her own distinct—and often highly idiosyncratic—way. Twenty years later, Jennifer Senior, a family friend and award-winning reporter, revisits the McIlvaines, examines their present lives, and contemplates what grief really means, in all its jagged complexity.