Poor, sad Lady Edith. Early on in “Downton Abbey,” the PBS “Masterpiece Classic” family saga, it seemed that the much-overlooked, undervalued middle sister of the Crawley clan had been dealt a rough hand. Her assertive nose, wan manner and decorously dowdy wardrobe had apparently rendered her marriage prospects slim to nil. Be kind to her, she has so few advantages, Lady Cora, her mother, urges Edith’s sister Mary. To which Mary peevishly replies that Edith has none at all.

That was then.

Turns out Season 4 of “Downton Abbey,” now in progress, has introduced a major shift in plot — the freshly bereaved Lady Mary sheds her widow’s weeds to mind the estate and field a few suitors, and Edith whisks herself off to a new life in London — and a shift in style as well. As the time frame moves to the racier 1920s, that change is expressed nowhere as vividly as through Lady Edith, who casts off her puff-pastry fashion persona to emerge as a maverick with real flair.

As Edith is sharply aware, there can be an upside to having no advantages. You are free to invent a few of your own.