Ann Brashares' best-selling novel for young adults comes to the big screen in this engaging comedy drama. Carmen (America Ferrera), Bridget (Blake Lively), Lena (Alexis Bledel), and Tibby (Amber Tamblyn) are four teenage girls who have been close friends since they were babies (and even before -- their mothers all knew each other from attending the same prenatal exercise class).
However, fate has dictated that for the first time ever the young women will be spending their summer apart -- Carmen will be visiting her father, whom she hasn't seen in years, Lena will be visiting her grandparents in Greece, Bridget is attending a soccer camp in Mexico, while Tibby is stuck working at a discount store. A few days before Carmen, Lena, and Bridget leave, the four go shopping, and while at a thrift shop they discover an unusual pair of blue jeans that, despite the fact they're all of different height and weight, fits all four women perfectly. The girls buy the jeans and pledge to each look after them for a week at a time, hoping they'll bring one another good luck as the girls deal with a variety of new life experiences, both good and bad.