The Ganges has existed at the heart of Indian culture for millennia. Long considered the mother of the subcontinent, it gave rise to one of the greatest early civilizations, with vast hubs of learning and culture that rivaled contemporary equivalents in China, Egypt, and Greece. But India's great river is in crisis, severely polluted by the 450 million people that live in its catchment area, and by the unfiltered human and manufacturing waste that runs daily into its waters. This in-depth portrait by the BBC's Justin Rowlatt uses images, video, audio, and narrative text to examine the current state of the Ganges, from its origins in the Himalayas to the leather factories of Kanpur to the burning ghats of Varanasi. Along the way, readers will enter the cities and farms through vivid photography and hear the stories of the people who make the banks of the River Ganges their home.