Whichever way you look at it, it seems that the taut lines of borders vibrate to the sound of world events, or even call them. There are more borders in the world today than ever before in human history. Starting with the oldest known example, Crawford travels to many old and new borders: from a melting glacial landscape to the troubled West Bank to the fault lines of the U.S.-Mexico border. He follows the history of borders to our fragile and uncertain future, to the virtual frontiers of the Internet and the changing geography of a world beset by climate change. As nationalism, climate change, globalization, technology and mass migration collide with increasingly rigid borders, something has to give. And Crawford asks: is it time to abandon the lines that divide us?