Lizzie and Frances, identical twins nearing forty, have hardly marked a parallel progress together through life. Lizzie is confident and effusive, married, the mother of a large, vibrant brood, a successful gallery owner, and a consummate homemaker. Frances, on the other hand, is as elusive as Lizzie is accessible: She lives alone, operates a modestly successful travel agency, and has never had a serious attachment to a man. It seems, to her loving family, as if Frances is destined to move through life anchorless.

But all that changes one Christmas when Frances makes an impulsive trip to Spain. There she falls in love—and not with just any man but with a wealthy, handsome, and married Spaniard named Luis, who, because he is Catholic, will never leave his wife. As Frances blossoms with newfound independence and relishes her engrossing affair, Lizzie becomes detached from her home life, which ultimately threatens her marriage. Though Lizzie’s was once the enviable life, now Frances has come into her own, and the twins must reexamine their roles—in their individual lives and in the special, shared world of sisterhood.