It took only 18 minutes for the Cunard liner Lusitania to sink after the German submarine U-20 torpedoed it off the coast of Ireland on May 7, 1915. From this blink of history’s eye, Diana Preston has pieced together an adventure story as intriguing and convoluted as the most cunningly fashioned spy novel. She weaves her dramatic tale from a close reading of hundreds of eyewitness accounts, newspaper reports, court records and related sources.

To put the tragedy in context, Preston first sketches the evolution of the submarine as an instrument of war and notes the resistance it met initially from home military establishments. Nonetheless, when World War I started in 1914, Great Britain had a fleet of 75 subs in service, and Germany had 28. The latter country’s underwater boats, however, were superior and deemed essential to breaking the crippling blockade Britain had imposed. Into this deadly new twist of warfare sailed the luxury liner Lusitania a carrier of civilian passengers, according to England, but a vessel with military significance by German standards. Well before the Lusitania set out from New York on its final voyage, German submarines had been sinking supposedly civilian boats near England. So open were Germany’s intentions on this point that its embassy placed an advertisement in American newspapers warning passengers that they traveled on British ships at their own risk. Most Lusitania passengers, while aware of the warning, accepted the Cunard company’s argument that the ship was too fast and would be too well protected when it reached home waters to be in danger. From such well-known figures as socialite Alfred Vanderbilt to lowly members of the ship’s enormous crew, Preston fleshes out the characters of many of the liner’s passengers. The author also takes us up to the Lusitania’s bridge to become acquainted with the dour, old-school captain, William Turner, and down into the dark and stifling bowels of the U-20, where its relentless commander, Walther Schwieger, waits for his prey.

As vivid as Preston’s descriptions are elsewhere, they rise to the level of poetry when she describes the chaos and elegant acts of heroism that occur as the great ship goes down. The scenes in the water as friends are separated and mothers lose their babies are heartbreaking. Still, Preston is admirably even-handed, refusing to depict the Germans as villains and enabling us to see the reasonableness of their actions from their point of view. The sinking cost 1,198 lives, 128 of them American. While this slaughter provoked an outcry in America, which was still officially neutral, it did not immediately draw the country into war against Germany. That would not occur until nearly two years later. And many more sinkings lay ahead.