The Ganges is one of the greatest rivers on Earth, but it is dying. From the icy Himalayan peaks, where it begins, right down to the Bay of Bengal, it is being slowly poisoned. The Ganges is revered in India but it is also the sewer that carries away the waste from the 450 million people who live in its catchment area. Pollution from the factories and farms of the fastest-growing large economy in the world – and from the riverside cremation of Hindu true believers - has turned its waters toxic. The Indian Prime Minister, Narendra Modi, promised two years ago to clean up the Ganges, but can he do it? Can the sacred mother of Hinduism be saved?