Through stories of two amazing individuals, a neurobiologist explains how we see and hear. That newborns must learn to talk is old news, but Barry, professor emeritus of biology and neuroscience at Mount Holyoke College, points out that newborns come into an incomprehensible world. Their eyes detect shapes and colors, and their ears hear sounds, but nothing makes sense. Over their first few years, babies literally discover how to see and hear, after which their ability to do so plummets. Doctors have long known that children who have sight restored after being blind throughout childhood never regain full sight. The same is true for hearing in congenitally deaf children. Until recently, writes the author, “few attempts were made to restore vision or hearing in congenitally blind or deaf people older than eight years. By age eight, the brain, it was thought, was no longer plastic enough to allow for the development of a new sense.” Yet exceptions exist, and Barry delivers gripping accounts of two. The first, Liam McCoy, lived in a “cocoon of visual blur.” At age 15, surgeons inserted a second lens into his eye (keeping the original), which vastly improved his vision. The result was not a familiar scene but rather a “tangled, fragmented world” of colors, lines, and edges. Barry devotes the first half of the book to the five years during which Liam gradually made sense of his new world. The second, Zohra Damji, was profoundly deaf. She was fortunate in that the condition was diagnosed very early and that her extended family provided intense support and the large sum of money required for the cochlear implant she received at age 12. Her first experience with sound was “loud, scary, and uncomfortable” as well as incomprehensible, but she ultimately sailed through graduate school. Both stories are inspiring and well rendered by the author. Even science-savvy readers will find surprises in this insightful exploration of how two humans learned a new sense.