Inspired by a profound experience swimming with wild dolphins off the coast of Maui, Susan Casey set out to learn everything she could about these creatures. Her journey takes her from a community in Hawaii known as "Dolphinville," where the animals are seen as the key to spiritual enlightenment, to the dark side of the human-cetacean relationship at marine parks and dolphin-hunting grounds. Along the way, Casey recounts the history of dolphin research and introduces us to the scientists and activists who have made it their life's work to increase humans' understanding and appreciation of the wonder of dolphins—the other most intelligent lifeform on the planet.