From Neal Stephenson, the #1 New York Times bestselling author of Polostan and Cryptonomicon, comes the second installment in his monumental Bomb Light series—a gripping tale set on the eve of World War II, as nations race to find and control an elusive substance critical to building atomic weapons.

Europe, 1934. British journalist Owen Crisp-Upjohn is dispatched to Moscow, where his assignments quickly escalate from cultural reporting to international espionage. Before long, Owen finds himself pulled into the orbit of the enigmatic Earl of Suffolk, a maverick aristocrat, and Aurora, a curiously compelling woman with a shadowy past rooted in Soviet intelligence.

Their mission soon becomes clear: secure the earth’s only supply of deuterium—"heavy water"—before it falls into Nazi hands. The high-stakes pursuit takes them from London’s plush drawing rooms to Barcelona, ravaged by the Spanish Civil War; from far-flung Soviet aerodromes to the perilous, icy landscapes of occupied Norway. Over time, Owen evolves from a detached observer into a man forced to confront profound questions of honor, love, and moral responsibility as loyalties are tested and allegiances shift in an ever-tightening web of science, intrigue, and deceit.

Rich with historical insight, emotionally complex characters, and a relentless sense of urgency with a world on the edge of cataclysm, D: Heavy Water is a suspenseful and wildly entertaining tale of courage and consequence in which humankind’s future is shaped by decisions made in the shadows.