For Fall, Ashley and Mary-Kate Olsen rented an empty Upper East Side town house and filled it with an eclectic array of furniture and objets. For an idea of how complete a world they conjured up for The Row this season, consider this: When the last model click-clacked her way up the stairs on her red mules, her imaginary dinner party over, the soundtrack was filled with children giggling at the return of Mommy. Here's another example: The foundation of each layered outfit was a ribbed knit onesie that peeked out of necklines and at the hems of cropped pants, a delightful indulgence that customers in colder climates just might take them up on next fall.

The Olsens care deeply about the details. Close study of the clothes revealed not just those underpinnings but pearls suspended from the collar of a black and white mink coat and brooches, from a Sidney Garber line designed by Brooke Neidich, sprayed across the revers of a single-button jacket. The designers developed many of their own fabrics this season. The white foulard silk jacquard they used for a V-neck sack dress was subtly spectacular.

But the duo also sees the big picture—probably because they wear the collection. More so than in recent seasons, they've begun to propose clothes for life beyond the office, cocktail, and dinner party circuit. In the mix were pieces that women will reach for again and again: a substantial fisherman knit with exaggerated sleeves, another great sweater with oversize proportions, statement outerwear like a heavyweight black leather jacket with a white Persian lamb collar and inset detail on the back.

"Without it being easy, we wanted it to be easy," Mary-Kate said afterward. A koan for the ages, but when you got to thinking about it, she summed up this collection's considerable appeal perfectly.