Five hundred years ago, in an alternate Age of Exploration, the earth is flat. Alchemy is a true science, sea monsters menace the oceans, and Europe is embroiled in religious controversy. At the edge of the world, where the stars reach down close to the Earth, wonders abound. This drives the bravest explorers to the beckoning Western Ocean.

Christopher Sinclair is an alchemist who cares only about one thing: quintessence, a substance he believes will grant magical powers and immortality. And he has a ship.

Fleeing an inquisition, physician Stephen Parris follows Sinclair to an island...