Plot
Lena Kaligaris, Tibby Rollins, Carmen Lowell, and Bridget Vreeland are teenagers from Bethesda, Maryland, who have been best friends their whole lives and are about to spend their first summer apart. Lena is visiting her grandparents in Santorini, Greece; Bridget is going to soccer camp in Baja California, Mexico; Carmen is visiting her father in South Carolina; and Tibby is staying home.
While shopping together, they find a pair of jeans that inexplicably fit them all perfectly. They decide to share the jeans equally over the summer, before parting the next day.
While wearing the Pants, Lena nearly drowns but local Greek boy Kostas Dounas rescues her. She later learns that her and his families are enemies. When Lena returns the shirt Kostas’ loaned her after the rescue, he explains the dispute was over money and fish. Their grandfathers claim to have cheated each other.
Kostas pursues Lena, insisting their families' dispute has nothing to do with them. She initially rebuffs his advances but eventually they have a secret relationship. When Kostas later tells Lena he loves her, her family interrupts and drags her away before she can answer. Lena’s grandfather spits in Kostas’ face and her grandmother berates her for breaking her promise to not see him again, as well as for her shirtless sketches of him. Lena appeals to her grandfather, insisting the dispute has gone on long enough so he lets her see Kostas before he leaves for Athens.
Working at a department store, Tibby finds young girl Bailey Graffman fainted and calls an ambulance. Later, Bailey delivers the pants to Tibby's when they are accidentally delivered to hers erroneously. Fascinated by Tibby's self-made film, Bailey appoints herself her assistant.
Initially annoyed, Tibby grows to accept Bailey, and learns she has leukemia. When Bailey again goes into hospital, Tibby initially avoids her, but eventually visits with the pants. Pleading with Bailey to take them, she insists they already worked their magic by bringing them together.
After they spend time together in the hospital, Bailey dies from her disease. Devastated, Tibby then decides to make a film inspired by and called “Bailey.”
Carmen arrives in South Carolina, only to discover that her white father Al is about to marry Lydia, who has two teens- Paul and Krista. They are all blonde WASPs, unlike Carmen, who is a Catholic, Puerto Rican. Although Carmen's father and step-family initially seem welcoming, they emotionally neglect her and act as if she is not there.
Carmen comes downstairs speaking Spanish assuming her father still understands her from his marriage to her mother, only to be told that nobody does. Her idea to make ethnic food for dinner with recipes from her mom does not interest them either. Carmen over hears Krista and her friend talk mockingly about her.
Carmen feels uncomfortable with her father referring to Paul and Krista as his kids, and resents his being an enthusiastic and present father to them while he has been largely absent from her life. She is embarrassed at a dress shop when she tries on the bridesmaid dress picked out for her for the wedding, as it is way too small. Angered when the saleswoman calls her "the other one", Carmen shouts at everyone and runs away.
Carmen eventually returns home and sees Al and her step-family happily enjoying dinner together in their dining room, apparently unconcerned that she was missing. Enraged and at her breaking point she breaks their dining room window and returns to Maryland. When she arrives, Tibby tries to help Carmen with her feelings toward her father. Carmen lashes out at Tibby, who leaves in tears, though they eventually reconcile. Tibby convinces Carmen to confront her father with a phone call, during which she finally reveals her feelings of neglect and abandonment. He apologizes sincerely, but Carmen tells him it isn't good enough.
Arriving at soccer camp, Bridget develops a crush on coach, Eric Richman. Despite relationships between coaches and campers being forbidden, Bridget flirts with Eric and seeks his attention during games. When Bridget's turn with the Pants begins, she leads Eric to the beach at night where they have sex and she loses her virginity. Bridget becomes depressed afterward lamenting that “how can something that should have made her feel whole make her feel so empty?” and isolates herself when she returns home. After hearing about what happened in a letter, Lena calls Carmen and Tibby, and they go to Bridget's house. Bridget worries she is like her mother, whose mood swings and mental issues culminated in deep depression and her suicide. However, Carmen and Tibby reassure Bridget that she is stronger than her mother and comfort her with happy memories of her mother. On his way back to Columbia University, Eric visits and apologizes to Bridget for his behavior and expresses his hope that she will give him a chance when she is older.
The girls meet Lena at the airport and drive to South Carolina to attend Carmen's father's wedding, despite Carmen's reluctance. Carmen's father publicly apologizes for neglecting her. Carmen accepts his apology and joins the blended family onstage for the ceremony.
