PARIS — Why did Pablo Picasso walk by the Galeries Lafayette on Jan. 8, 1927? Was he heading back to his home in the upscale 8th arrondissement of the French capital? Or was he going to the department store to buy a gift for his wife Olga, or a toy for their son, Paulo?

And why was the young Marie-Thérèse Walter at the same place at the same time? Word is that it was because her mother, a milliner, worked in the neighborhood.

They ran into each other. And then Picasso, after introducing himself, is believed to have told the young woman: "Mademoiselle, you have an interesting face, I would like to do your portrait." Next. he supposedly said, "I feel we're going to do great things together," a remark almost too prophetic to be true.

An interesting face and an interesting body: Judging by photographs dating back from when they met, Marie-Thérèse looked like those athletic women with wide shoulders and slender legs that Picasso later painted in his sculptural fashion.

We could deduce from this that Picasso saw in her a form of beauty that was familiar to him, which would begin to explain this singular but decisive encounter in the painter's life and works, as the exhibition "Picasso 1932. Année Érotique" at Paris's Musée Picasso shows.

The exhibition has three protagonists: Olga, Marie-Thérèse and Picasso. In boulevard theater these would be the wife, the mistress and the unfaithful husband, but more analytically, they are the artist and his two models, the old and the new.

The exhibition is interesting because it alternates between two stories, biographical and artistic. It follows the 366 days of the leap year 1932 in the lives of these three people and those around them: poets, shopkeepers, hoteliers and suppliers. Reconstructing this day-to-day chronicle required collecting a plethora of bits and pieces. As it happens, Picasso never threw away anything, and the museum has kept dozens of boxes stuffed with bills, press clippings and letters. This has made it possible to present a very precise story. Among the canvasses, the drawings and the engravings are display cases showing various documents, each more enlightening than the next.

Clues to a life split between wife and mistress

Museum goers who might not have two or three hours to spend on their visit should look at the sad articles by French critics who that year denounced Picasso as the culprit for the decadence of French good taste, reviews that paved the way for Nazi propaganda against "degenerate art." For the opposite reason, visitors should also read the attentive letters and articles from foreign curators and critics about the Picasso retrospective held that fall at the Kunsthaus in Zurich.

In the archive are also clues to a life split between wife and mistress, who would later give birth to Picasso's daughter, Maya, in 1935.

Picasso showed all the external signs of an exemplary life: his son's communion at the St-Augustin church in Paris followed by a visit to the Sacré Cœur, family vacations by the sea, photos showing Mrs. and Mr. Picasso at the Château de Boisgeloup, where he would later create sculptures glorifying Marie-Thérèse.

In 1932 Picasso was still able to visit Marie-Thérèse secretly. This would not have been the case had Olga discovered one of the photographs, now exhibited at the museum, of Marie-Thérèse on the beach, which the mistress sent her lover during the summer, along with letters in which she told him about her days at Juan-les-Pins. These photographs were transformed by the Picasso mental and visual machine into erotic allegories.

This would never have happened had Olga paid closer attention to her husband's work: She would have suspected something was going on had she observed his new fashion of drawing and painting. This new fashion was the Marie-Thérèse language, which Picasso began inventing in 1927, and which in 1932 became the language of his visual poems in honor of the young woman.

The primary signs of that language are the circle, the oval and the sinuous line. One following the other, they depict a face, breasts, arms and hips in curved stylization that form identifiable shapes, even if disproportionate.

These shapes are usually painted in one color with little modulation, or are sometimes enhanced with a smear of white. Sometimes they are harmonies in three tones — grey, almond green and purple — sometimes resounding chromatic orchestrations: Le Repos, dated Jan. 22, Girl before a Mirror, completed on March 14, and Femme couchée à la mèche blonde, from Dec. 21, which seems to announce the most unbridled nudes of Picasso's last years.

He would sketch these anatomical designs on paper, either with a pencil or with ink. Several tests would ensue until one formula emerged, which Picasso would then reproduce on canvas. Except he would not reproduce it as it was. Instead, the drawing would change as he painted it and as color ratios suggested new transformations.

Here too, it would take hours to examine each moment of this experimental method, day after day, hour after hour, from notebooks to canvases. For the exhibition, several sequences have been reconstructed, not entirely but with enough detail so that visitors can follow the process and understand how it worked.

One of these sequences is not dedicated to Marie-Thérèse but to Matthias Grünewald's Isenheim Altarpiece. Although Picasso traveled through Alsace on his way to inaugurate his exhibition in Zurich, he did not stop in Colmar, where the retable is kept, but instead worked from reproductions.

Beyond that, the method is the always the same, be it with the secret mistress or the crucifixion. One study after another, with the second developing a suggestion that appeared in the first, and so on. Although the process remains the same in both cases, Picasso's language is profoundly different. It is no longer that of an erotic ballad but that of tragedy and death, of a martyred body, dismantled skeletal structures, black and white. Picasso's crucifixion from 1932 is Guernicafive years before Guernica.