Stefano Pilati consolidated his Spring breakthrough with a sensational new collection for Yves Saint Laurent that was as tightly controlled as the models' chignons. Backstage, he listed a whole lot of years he'd been looking at in the house archives—from 1962 to the late seventies—but history was ultimately irrelevant in the light of the results. Yes, the double-breasted coat-dress in the Prince of Wales check, clasped at the waist with a half-belt, ending at mid-thigh, had an early-sixties precision, just as the sweeping palazzo-panted volumes of the finale reeked of late-seventies fabulousity, but Pilati distilled decades into a single strong statement that spoke of the here and now. On some level, it probably worked because he's successfully isolated the genes he shares with Yves, which meant there was more instinct at work than before. But no need to try to get inside Pilati's head; suffice it to say that these were rigorously elegant, superchic, and sexy clothes.

In his pre-fall collection, the designer was inspired by YSL's "Opium" era. He claimed he didn't want to let that go, hence the vintage Bianca Jagger moments in this show. But his experience with his Fall menswear was also significant. The lean, boyish silhouette of that outing clearly influenced Pilati's experiments with the most familiar codes of haute bourgeois dressing—a skirtsuit, sweater, and pants; fabrics as classic as a dogtooth or a Prince of Wales check. He dissected them: deconstructing, reconstructing, exploding patterns but, for the most part, keeping dimensions ultra-lean. The monochrome palette helped. Colored sequined motifs were an unnecessary distraction, especially in comparison to a look as tensely sensual as the cape over a sleeveless jumpsuit with a halterneck in chiffon.

The final sequence came in blinding white. A blouse stock-tied at the neck, full-sleeved, paired with a skirt falling decorously to the knee, was totally see-through. Freja Beha Erichsen's final outfit—a huge marabou bubble, a sheer blouse with a collar that was almost clerical, palazzo pants bound by a big glittering bow at the waist—struck a balance between sacred and profane. That kind of equilibrium seemed like the essence of YSL—and Pilati, too.