Every now and again, a fashion mood emerges that should work particularly well for certain designers. Sometimes, they hit their stride and get it right during that period; sometimes, they don't. Stella McCartney's spring collection put her firmly into the former. She took what has been slowly emerging in Milan and Paris—pastoral, romantic dressing, and a sharper, speedier sportswear aesthetic—and spliced them together. It's not that she hasn't tried to do this before, but this season it just all came together. Better still, she hit on some of the other key trends—safari jackets; slouchy, straight-cut cuffed pants; and breezy, billowing dresses—and effortlessly made them her own.

McCartney is most convincing when it looks like the clothes belong in her world, not to mention her closet. Previous seasons have featured pieces that were a little too tricky for their own good: If you can't imagine her wearing it, then it's not going to fly. But this time round, McCartney played to her strengths: A smidge of vintage (floaty floral chiffon dresses), a touch of lingerie (camisoles and bras used to good effect layered underneath tops or dresses), pretty tailoring (shrunken jackets over those loose pants). And she made the strongest case for tiered gypsy skirts, letting them swoosh along the runway in white cotton muslin, as delicate as Edwardian underwear.