When Bonnie J. Rough receives the test results that confirm she is a carrier of the genetic condition hypohidrotic ectodermal dysplasia, or H.E.D., it propels her on a journey deep into her family's past in the American West. At first glance, H.E.D. seems only to be a superficial condition: a peculiar facial bone structure, sparse hair, few teeth, and an inability to sweat. But a closer look reveals the source of a lifetime of infections, breathing problems, and drug dependency for Bonnie's grandfather Earl, who suffered from the disorder. After a boyhood as a small-town oddity and an adulthood fraught with disaster, Earl died penniless and alone at the age of forty-nine. Bonnie's mother was left with an inheritance that included not just the gene for H.E.D., but also the emotional pain that came from witnessing her father's misery. As Bonnie and her husband consider becoming parents themselves, their biological legacy haunts every decision. The availability of genetic testing gives them new choices to make, choices more excruciating than any previous generation could have imagined. Ultimately, Carrier is a story of a modern moral crisis, one that reveals the eternal tension between past and future.