Marguerite Harrison first came to my attention in 1993, when I was doing research for a biography of the British official Gertrude Bell. The formidable woman had written a letter from Iraq telling about an American who had come through Baghdad after World War I.

“She is an exceptionally brilliant woman,” Bell wrote, adding that she had come to dinner and “I never had such an uproarious dinner party.”

What, I wondered, was an American woman doing in Baghdad in 1924? And what had made her so interesting? I was certain she must have been a spy.

An Unlikely Story

Marguerite Harrison was the daughter of a Gilded Age shipping tycoon and his society wife. In 1901, Harrison married a handsome stockbroker who had more charm than money. A year later they were the parents of a son and she was a Maryland socialite who favored fashionable clothes and children’s charities.

Harrison with Merian C. Cooper, a photographer assigned to illustrate her newspaper stories.

Her husband died unexpectedly and left her a widow in debt at 37. To cover her expenses, she took a job at The Baltimore Sun and was promoted to the position of reporter. When the U.S. entered the Great War, she was eager to go to the front, but women were forbidden. Undaunted, she applied to the military to be a spy.

At the National Archives, in Washington, D.C., I discovered Harrison’s classified military-intelligence files, which revealed that she had spied for the U.S. in Russia and Germany. Many cables referred to the risks she was taking, the danger she was in, the courage she showed. In the secretive Cheka files, in Moscow, I found transcripts of her prison interrogations.

I was awed by her daring, whether ducking gunfire in the streets of Berlin or traversing precipitous mountains in Persia. She told of traveling on rickety ships, sleeping with bedbugs, confronting robbers in the Syrian Desert, and sneaking across hostile borders at the risk of death. Nothing seemed to stop her. She seemed fearless. Was she playing a game?

The moment of truth came in Moscow when she heard a knock on her door. “I suppose you are here to arrest me,” she said calmly to the Cheka police. They showed her their orders, searched her room, and drove her off to the dreaded Lubyanka prison.

Harrison, center, attended by two members of a Persian expedition she reported on.

The sentry led her to the door of a dingy, dark cell. She stepped inside and heard the door slam and the key turn in the lock. Cut off, she was in solitary confinement.

What, I wondered, was an American woman doing in Baghdad in 1924?

On the walls, Harrison made out the words of men waiting to die. One Frenchman had scrawled: “Rira bien qui rira le dernier.” (“He laughs best who laughs last.”) A Russian wrote in Cyrillic: “Now I’ve told everything. This is the end.” She panicked—she, too, was waiting for the end.

She could guess the time only by the actions of a guard outside: the switching on of a light bulb every 30 minutes; the clicking of the peephole, “an instrument of terror” he opened to watch her dress and undress; the delivery of a meal, a fish eye staring out from a bowl of watery soup.

She heard the frantic cries of people barred from the bathroom and the harrowing screams of prisoners taken out to be shot. Depression engulfed her. She was Prisoner 2961—meaningless, a single figure among thousands trapped by the Bolshevik Revolution.

A view of the Lubyanka, the Soviet K.G.B. headquarters and prison in Lubyanka Square, Moscow, 1963.

Harrison had no one to talk to and nothing to do but brace herself against the agony of isolation. She realized the only thing to keep from going mad was to stay busy in her present life. She made a schedule and concentrated on her routine: cleaning out vermin, sweeping the floor, testing herself on history, walking back and forth 500 times twice a day in her tiny cell.

The hours crawled on. Desperate after seven days, tortured by the silence and afraid of losing her mind, she asked for pencil and paper and wrote to her interrogator. “I have an important communication for you,” she said.

Two hours later they met. What was it she had to tell him? he asked.

She couldn’t take it any longer—she confessed.

“I need hardly tell you why you are here,” he reminded her.

“We have been playing a game,” she answered, “and I have lost.”

A guard came and took her away.

Harrison spent a total of 10 months at Lubyanka, where she contracted tuberculosis. She was eventually set free, and went on to write several books about her experiences there.

Janet Wallach’s Flirting with Danger: The Mysterious Life of Marguerite Harrison, Socialite Spy is out now from Doubleday