Sara Louise and Caroline Bradshaw are twins who grow up on a tiny Chesapeake Bay island in the 1940's. While Caroline is musically talented, beautiful, and socially popular. Sara Louise is a tomboy who enjoys crabbing with her friend, McCall Purnell, who is a year older than her.
When we first meet Call, he is an overweight and bespectacled 14 year old. He goes crabbing with Sara only because his father has passed away and he no longer has an opportunity to be taken aboard a proper crab boat. When Sara thinks that the old man who has just moved into the Wallace place is a spy rather than old Hiram Wallace, she enlists Call's help to check the man out. Even though Call is skeptical about Sara's claim, he goes along with her scheme. The novel delineates Call and Sara's early friendship as that between two childishly innocent partners-in-crime.
However, the relationship soon changes as Sara starts to mature. With Caroline perpetually favored as the more accomplished sister, Sara has no choice but to live under the shadow of her sister's overpowering charisma and beauty. Equally awkward in her social presentation and feminine persona, Sara is often self-conscious. She is bitterly protective of her friendship with Call; after all, Call is the only one who seems to accept her. He does not mind that she is a tomboy. When Call invites Caroline along to visit Captain Hiram one day, Caroline accepts and asks Sara whether she would like to go as well. Sara's thoughts are illuminating:
Who did she think she was, inviting me to go see the Captain? As if she owned both him and Call. Call, who had always belonged to me because nobody else besides his mother and grandmother would have him...
As time passes and Caroline goes off to New York to attend the Julliard School Of Music on a full scholarship, Sara finds herself at a crossroads. Should she choose marriage or should she go off to college as well? If she chose marriage, who besides Call would marry her? When WWII starts, Call enlists in the Navy. After the war, Sara is shocked to find that her old friend is no longer the Call she remembers:
He stood there in his petty officer's uniform, tall and almost shockingly broad-shouldered and thin-hipped...
With this discovery, she finds unknown emotions and foreign sentiments stirring within herself. However, her emerging hopes for possible happiness with Call is rudely disappointed when she discovers to her dismay that Call has chosen her very feminine sister as his intended wife. At the moment of Call's announcement that Caroline has accepted his proposal of marriage, Sara knows that her relationship with her old friend will never be the same again. The old, easy camaraderie will forever be lost now that Call is to be married to Caroline.