

She was right. That morning the president had seen aerial photographs that showed the Soviets installing missile bases in Cuba. The worst crisis of the Cold War was about to begin.

Susan Mary had always liked to see "history on the boil," as her friend the English novelist Nancy Mitford once put it. And as the French diplomat Caroline de Margerie shows in this tale of privilege, "American Lady: The Life of Susan Mary Alsop, " she had a ringside seat during the Kennedy administration. The parties she gave with her newspaper-columnist husband were the center of the political scene in Washington. Over the years her friends included Winston Churchill (who liked to converse with her in his fluent but unintelligible French), Henry Kissinger, the French intellectual Raymond Aron, Evelyn Waugh, Isaiah Berlin and even that dubious couple, the Duke and Duchess of Windsor.

As a young woman, Susan Mary (1918-2004) had been fascinated by the world of politics, but she lived in a time when virtually the only way for a woman to participate was to make friends with powerful men. Intelligent, earnest and ambitious, she educated herself in current events and history and excelled at working a room. "Sidling up to the man she had singled out," Ms. de Margerie writes, "she would engage him in conversation. Her voice would descend a pitch, her brows furrowed with interest, and she would tilt her head in a pose of absorption. Fingering her pearls, she would murmur, 'How fascinating.' "

It helped that she had the right sort of background. Susan Mary was a descendant of John Jay, a Founding Father and the country's first chief justice. She grew up in Washington and New York, with summers spent at the family estate in Maine. At 21, she married Bill Patten, a Boston stockbroker nine years her senior. Her life might have been limited to husband, children and bridge parties had not Patten accepted a job at the American embassy in Paris in late 1944.

From that point, Susan Mary's life seems straight from the pages of a Henry James novel. Innocents abroad, the Pattens stumbled into the Paris court of the British ambassador Duff Cooper and his wife Lady Diana, a world of weekend picnics on the grounds of houses the size of Versailles, masked costume balls and passionate relationships carried on under a veneer of propriety. Duff was a brilliant intellect and a profligate seducer. "Women, literature, and politics were the three interests that occupied Duff's time in equal proportions," writes Ms. de Margerie. "His technique was to compose sonnets and seal the deal."

American Lady

By Caroline de Margerie
(Viking, 232 pages, $26.95)

One evening Lady Diana, who famously ignored protocol and mixed her guests without regard to rank or status, seated Susan Mary next to Duff at a dinner. The two began a six-year liaison during which she had a son by him, which neither acknowledged. Ms. de Margerie maintains that Patten never knew of the affair, but a line Duff wrote in his diaries three months after their son's birth makes me wonder: "It now seems that last spring Bill made her a great scene of jealousy about me. I had no idea of it."

Susan Mary believed Duff was the love of her life, yet four years after his death, on New Year's Day 1954, she took up with another British diplomat, Gladwyn Jebb, a man she had once dismissed in a letter to Duff as "a cold poached egg type." Ms. de Margerie makes no comment except to say that, when it came to love, Susan Mary "was an Anglophile and walked on Pall Mall."

Even Henry James couldn't have imagined Susan Mary's next step. When Bill Patten died of emphysema in 1960, she returned to Washington, where, within the year, she married his Harvard roommate Joseph Alsop, knowing that he was gay. The marriage gave Susan Mary a powerful position in Washington, while for Alsop she was a beard and the hostess he needed for his parties. She was dubbed "the second lady of Camelot," and during the gilded Kennedy era, the Alsop circle had remarkable influence and prestige.

Soon after the death of Kennedy, however, the marriage began to fall apart. Alsop was a tyrant, and conversations at the dinner table became a nightmare as he drank, shouted and raved while his wife looked on in martyred silence. They divorced in 1973, and Susan Mary summed it up in a letter to her son: "Having loved him and fought for him was a waste of fourteen years." She moved out of the house, but they remained friends, and for the next 30 years she was a formidable D.C. hostess in her own right. She also turned her hand to writing and published, among other things, a volume of letters she had written during her 15 years in Europe. They were inspired, Ms. de Margerie says, by Janet Flanner's "gin-soaked columns" about Paris for the New Yorker. They are lively and perceptive about politics but, not surprisingly, reveal next to nothing of the emotional turmoil Susan Mary went through during those years.

One of the more astonishing scenes in "American Lady" takes place in 1995 at a rehabilitation center in Minnesota where Susan Mary, now an alcoholic, was taken by her children. Urged on by a therapist, she tells her 47-year-old son "in an almost detached tone" that his father wasn't Bill Patten, as he had been raised to believe, but Duff Cooper, sending him sobbing out of the room. Why she did this is a mystery, but Ms. de Margerie notes that she must have felt an angry satisfaction in causing chaos after the embarrassment of being committed to a treatment center.

"American Lady" was first published in France where it was subtitled "a reporter in white gloves," and, alas, the gloves are never entirely removed in this slim but entertaining biography. There was a great deal on the boil besides history in Susan Mary's life. But she gave little away emotionally, and in the end she remains an enigma.

Ms. Hodgson is the author of "It Seemed Like a Good Idea at the Time: My Adventures in Life and Food."