This is the story of one lost poem, two great rivers, and three remarkable lives - all connected by a single drop of water. In the ruins of Nineveh, that ancient city of Mesopotamia, there lies hidden in the sand fragments of a long-forgotten poem, the Epic of Gilgamesh. In Victorian London, an extraordinary child is born at the edge of the dirt-black Thames. Arthur's only chance of escaping poverty is his brilliant memory. When his gift earns him a spot as an apprentice at a printing press, Arthur's world opens up far beyond the slums, with one book soon sending him across the seas: Nineveh and Its Remains. In 2014 Turkey, Narin, a Yazidi girl living by the River Tigris, waits to be baptised with water brought from the holy sit of Lalish in Iraq. The ceremony is cruelly interrupted, and soon Narin and her grandmother must journey across war-torn lands in the hope of reaching the sacred valley of their people. In 2018 London, broken-hearted Zaleekhah, a hydrologist, moves to a houseboat on the Thames to escape the wreckage of her marriage. Zaleekhah foresees a life drained of all love and meaning - until an unexpected connection to her homeland changes everything.