In Victorian London, an extraordinary child is born at the edge of the dirt-black Thames. When his brilliant memory earns him a spot as an apprentice at a printing press, the world opens up far beyond the slums and across the seas. In 2014 in Turkey, Narin, a Yazidi girl living by the River Tigris, waits to be baptized. The ceremony is cruelly interrupted, and soon she and her grandmother must journey across war-torn lands in the hope of reaching the sacred valley of their people. In 2018 in London, broken-hearted Zaleekhah, a hydrologist, moves to a houseboat on the Thames to escape the wreckage of her marriage – until an unexpected connection to her homeland changes everything. A dazzling feat of storytelling from one of the greatest writers of our time, one that spans centuries and continents, this is the story of one lost poem, two great rivers and three remarkable lives – all connected by a single drop of water.