Sienna and Savannah Miller called their Spring collection Jericho, inspired by Joni Mitchell's album Don Juan's Reckless Daughter. Their road-tripping muse is a Kerouac-reading dreamer with an itinerary —fifties-era Mexico, Thailand, the Nevada desert, perhaps her native Texas. She's also got a hawk eye in vintage shops and ethnic markets. (Sound like anyone you know?)

There was a certain sunbaked nostalgia to the bibbed denim shirts, flounced cheesecake skirts, a fringed suede dress, and a canary yellow lace shift. Whether art imitated life or vice versa, Savannah actually sourced the paisley print that was cut into a poolside-bound halter dress at a vintage store in Colorado. In the end, though, the backstory was mostly a neat way for the Miller sisters to weave a little of everything they've long loved into their runway show. "I think we really crossed borders," said a chipper Sienna backstage. "There's something for the working girl, the casual girl, the festival girl, the London girl."

She's right, and there were clothes here you'd be thrilled to find on a retail rack. There are more and more of those these days as the sisters' reach grows—they open their third London boutique next month. Still, the question hangs in the air: Does a solidly contemporary line like Twenty8Twelve merit the runway spotlight? It's a debate that reached a peak in New York last week, where at one end of the spectrum you had the purposefully overexposed Zac Posen, with his Z Spoke "fashion-tainment" show, and at the other end, the deliberately withholding Tom Ford. Still, Savannah and Sienna might argue that the right you have is the right you take. They now seem utterly confident of their place, and sometimes that's all that's required.