Michael Ruhlman is fascinated by people at work-especially those in pursuit of perfection. The Soul of a Chefand Wooden Boatshave established him as a deft chronicler of unique cultural microcosms. Now, in Walk on Water, he documents life in the most intense environment yet-a pediatric heart center specializing in neonatal open-heart surgery. The precision needed for such delicate surgery puts "soul-crushing, diamond-making stress" on physicians and...