The narrator, a young boy from a small riverside town, recounts joining a country doctor who speaks to animals and their subsequent seaborne adventures. Together they assemble a diverse crew aboard the Curlew, visit remote islands, and study animal languages including shellfish and parrots. The voyage brings storms, shipwreck, encounters with strange peoples and beasts, a local war and a populist coronation that reshapes island life. After scientific puzzles, daring rescues, and humorous observations about human and animal behavior, the doctor faces a final choice about leadership and whether to return home.