BETWEEN SILK AND CYANIDE

A Codemaker's War 1941-1945

By Leo Marks

Free Press. 614 pp. $27.50

Reviewed by Ken Ringle

Just when we think all the great stories of World War II have been told, along comes Leo Marks to sandbag us with another amazing tale from the long-hidden world of cipher skulking that played such havoc with the Third Reich. Who knew, who would have even dreamed, that the chief British mind dreaming up codes for allied agents behind Nazi lines was barely 22 years old?

The intellect in question was Marks himself whose quirky, captivating memoir is alternately as suspenseful, mordant, hilarious and eloquent as his irresistible title would imply. He was, he tells us, the precocious only child of a noted antiquarian bookseller in whose famous premises at 84 Charing Cross Road Marks launched his cryptographic career. After warming to the subject by reading Edgar Allan Poe's code puzzler "The Gold Bug" when he was 8, he promptly decoded the curious scribblings on each book spine in the shop, which turned out to be his father's reminders, for bargaining purposes, of what each volume had actually cost.

Little more than a dozen years later, unaccountably overlooked by the cerebral dragnet that staffed the brilliant and fiercely eccentric code-cracking center at Bletchley Park, Marks ended up as head of communications for the Special Operations Executive (SOE) -- a Churchillian agency founded after the fall of France to "set Europe ablaze" with saboteurs and spies in preparation for the Allied invasion. The youthful prodigy promptly discovered that the agency's all-too-transparent codes were helping the Gestapo uncover the very Allied agents those codes were supposed to protect, and he set out to make changes. The special charm of his book is the impish delight with which he recounts his youthful maneuvers to that end within the stodgy bureaucracy of wartime Britain. The special power of his book is the reverence he shows still, half a century later, for the lives he once found in his care.

A tragicomic portrait emerges: the youthful cipher-sleuth, sent off to war each morning by the ultimate Jewish mother, armed with the choicest black-market foodstuffs with which he cheerfully disarmed his flavor-starved and ration-weary superiors. In the process he first devised and then managed to implement Nazi-proof codes to be hidden in scraps of silk underwear or in poignant, highly personal poems.

"Codes meant as much to me as Spitfires did to those who had guts," he explains, and one of the many illuminating aspects of Marks's memoir is how well he evokes both the intellectual subtlety at the top levels of the cryptographic war and the even more heroic intellectual drudgery at the bottom. Agents under pressure in the field often sent radio messages that were coded, transmitted or received with some error, leading early in the war to demands that they be designated "undecipherable" and ordered re-sent. But Marks realized that each retransmission was incredibly dangerous, exposing both the agent and the code he was using to the lethal consequences of Nazi detection. He managed to persuade his underlings -- hundreds of specially trained women known as the Field Auxiliary Nursing Yeomanry (FANY) -- that there could be "no such thing as an `undecipherable'," even if a garbled message required 5,000 to 10,000 attempts to unravel it. The everyday miracles of decipherment that this eventually involved stagger the mind.

Marks's brilliance clearly disturbed his SOE superiors as much as it served them, for, like any student smarter than his teachers, he was something of a rogue young elephant in the ranks of cryptography. He broke a French code he wasn't supposed to read in order to give French agents more protection than the French themselves thought necessary, and at one point he baited a trap with dummy information to unmask the successes of his German counterpart. When he discovered that most of the Allied agents operating in Holland were really being controlled by the Nazis, he couldn't get anyone to act on the information: It was out of his area of responsibility and would have called into question the judgment of others far older and "wiser" than he.

All of which makes his book sound like the exercise in payback and self-justification that so many memoirs become. Despite a taste of that, however, Between Silk and Cyanide repeatedly saves itself through its author's self-deprecating if affectionate portrait of the blithe and brilliant youth he used to be. He repeatedly paints himself as a physical coward struggling to atone with his wits for the terrible sacrifices made by others in the Allied cause. And the haunting sense of those sacrifices that stalks him with each agent's death fuels an obsessive hunt for better and alternative code systems: simpler and faster to use and harder to detect and break.

For those who know Helen Hauff's lovely book 84 Charing Cross Road, or the fine Anne Bancroft film made from it, there will be double pleasure in Marks's book -- a vastly expanded window into the literary universe she met and learned to love through her correspondence with a London bookstore. Many of Marks's superiors and other contacts in the code business turn out to have had bibliographic ties to his father's store in some way. Likewise, the dance of letters and images at the heart of codemaking turns out to be kin to those in the poems and stories he discovered in the literary treasure house where he grew up.

The author is only rarely quite as funny as he thinks himself to be, and he has an annoying habit of penning phrases ("The facts emerged slowly, like soldiers from a brothel") from which some merciful editor should have saved him. But despite such occasional distractions, Between Silk and Cyanide remains a welcome and powerfully affecting chapter of World War II history, and a very human story of the most clandestine and cerebral art of making war.

Ken Ringle, a reporter for the Post's Style section, has written extensively on World War II.