One of Washington's best kept wartime secrets has finally been revealed: the identity of the famous "Foreign Lady."

The mystery was born in Georgetown during the darkest days of World War II against the backdrop of a Nazi-dominated Europe. Its central figures are a poet and his muse, separated in occupied Paris and reunited here by the hazards of war. It is also a love story.

The poet was Saint-John Perse, a celebrated imagist and one of France's foremost diplomats, who would win the 1960 Nobel Prize for literature. The muse became the anonymous subject of his "Poem to a Foreign Lady," the only work by Perse that makes specific reference to any woman other than his mother.

More than 40 years of speculation on the identity of the "foreign lady" by Perse enthusiasts -- who include French President Franc ois Mitterrand -- has centered on a Spanish woman of aristocratic birth. There are several apparent references in the poem to Spain, including a phrase about the "green blood of the Castiles" beating in the foreign lady's temples.

But, as the result of some astute transatlantic detective work, it now turns out that the speculation was wrong. The foreign lady was a Cuban of great intelligence and seductive charm, Rosalia Sanchez Abreu, known to her friends as Lilita. The daughter of a wealthy Cuban landowner, Lilita had played the role of literary muse for the tight little Parisian world of writers and poets -- most notably playwright Jean Giraudoux, who fell hopelessly in love with her.

It was in Paris, probably in the '30s, that Lilita and Perse first met. Perse, whose real name was Alexis Leger, was bitterly opposed to the Vichy government's policy of collaboration with Nazi Germany and refused the post of ambassador to the United States. In October 1940, five months after the fall of Paris, he fled his homeland for what would become a 17-year exile in Washington. He was 52.

The following summer, Lilita, then 54, arrived in America by way of Portugal and Cuba. She found a little house in Georgetown at 3314 P St. Perse rented a small apartment a few blocks away at 3120 R St.

"Lilita was a fascinating woman," said Joseph J. Jova, an American relative of the Abreu family and former U.S. ambassador to Mexico. "She was a femme du monde. She had a magnetic personality, vital, willful. She was also very, very well-off."

In addition to being at home in Parisian literary salons, Lilita was also apparently something of a mystic. According to Jova, she caused a minor scandal while staying at a New York hotel by showing up with her Indian swami.

The unraveling of the poetic puzzle has coincided with the 100th anniversary of Perse's birth, which is being celebrated with great fanfare in France. It has already led to a reevaluation of the life and work of a poet known for his use of complex imagery and mastery of the melodic rhythms of the French language.

"Foreign Lady" takes the form of a dialogue between two exiles in a strange town. The "foreign lady," or "l'Etrangere" as she is known in French, feels lost in the New World, pines for Europe and is distressed by the suffering of her friends on the other side of the Atlantic. The poet, more open to America than she, holds out the hope of a better world once the war is over.

"Lilita was the only woman who really counted in Perse's life," said Sylvia Desazars de Montgailhard, who helped to solve the mystery. "I don't think there is much doubt that they were lovers."

The wife of a senior French diplomat in Washington, Desazars stumbled onto the real identity of the "foreign lady" as the result of her family connections with the Spanish and Cuban aristocracy. Her discovery was confirmed by the publication in France earlier this year of a series of letters from Perse that make it quite clear that Lilita is "l'Etrangere."

And, in a diary entry dated Aug. 15, 1942, that has recently come to light, Lilita noted: "I sat next to him {Perse}, on a little stool, and I began reading a very beautiful poem. I am the foreigner, the alien, who cuts herself off from the world with her memories ... "

Other recently discovered manuscripts show that Perse originally called his poem "P street." The title was later changed to "V street," which threw early researchers off the track because the "V" referred not to the foreign lady's address but to the hoped for victory that would end the war and allow both exiles to return home. "Poem to a foreign lady" was the third and final title.

The poem describes R Street in Georgetown as a "district of Hospices for the Blind, enshrouded reservoirs and encaged valleys for the dead ... and fine Italian gardens," all of which still exist. It also talks about the disused streetcar tracks on P Street, which, according to Lilita's notes, are a metaphor for "the inexorable march of time ... fueled by nostalgia, vain hopes, and lost memories."

There are several hidden clues to the foreign lady's Cuban origins, including two references to cigars. For an aristocratic Spanish lady to have smoked cigars would have been regarded as scandalous -- but it was quite acceptable for a Cuban woman like Lilita. There is also an allusion to a 16th-century painting by the Spanish artist Diego de Vela'zquez, which Desazars believes is an indirect reference to a Spaniard of the same name who conquered Cuba in 1511.

Ambassador Jova, who knew Lilita in this country, speculates that the Abreu family's Caribbean background may have been an additional point of attraction for Perse, who was himself born on the island of Guadeloupe in the French Antilles.

"It was another little bond that existed between them -- something that went beyond their common intellectual interests," Jova said.

The relationship between Perse, who died in 1975, and Lilith continued to her death in 1955 at the age of 69 after a long illness. Three years later, he married an American woman, Dorothy Milburn Russell.

Throughout his correspondence, it is clear that Lilita was a unique source of inspiration. In what could almost be an epitaph to the "Foreign Lady," the poet wrote about his feelings for her in a letter to his sister Eliane in 1953. He wrote: "I want her to know that she will always represent the best of myself ... and that, whether she is aware of it or not, the deeply human link that unites us will remain for me quite exceptional until my death."