Published in 1920 in the Saturday Evening Post, a popular magazine of the day, "Bernice Bobs Her Hair" deals with a favorite theme of F. Scott Fitzgerald's: the desire for popularity in the shallow, appearance-obsessed social climate of the famous "Roaring 20s."
As the story opens, Marjorie Harvey is getting sick of finding male companionship for her visiting cousin, the prim, boring Bernice. After an exasperated Marjorie confronts her with her social ineptness, Bernice meekly agrees to take any advice Marjorie has to give her.
Marjorie obliges, helping her with clothes and posture, and finally telling her a most important secret. A popular girl, she says, uses "lines," startling and slightly naughty conversation-openers.
Bernice tries it out and decides on her favorite: "Do you think I should bob [cut short] my hair?" At this time, short hair was seen as a sign of loose morals—no "nice" girl would do it. Soon, the newly confident Bernice is surrounded by fascinated boys.
Marjorie realizes that her advice has worked too well. The boy who once adored her, Warren MacIntyre, is now paying attention only to Bernice. Angry and jealous, Marjorie hatches a plan.
Next time Bernice uses her bobbed-hair line, Marjorie challenges her: will you really cut your hair, or are you just talking? Bernice is stuck. She has to prove that her "line" is not a line. She heads for the barber shop, accompanied by all of Marjorie's friends.
The result is a disaster. Bernice looks terrible in short hair. Moreover, her new look will offend the hostess of the next night’s party, a strictly religious woman who considers bobbed hair a sin.
Late that night, humiliated Bernice packs her bags and leaves. But not before she takes her revenge. While Marjorie sleeps, Bernice "scalps" her selfish cousin, cutting off her long, luxurious blonde braids.
In a final act of fury, she throws the braids onto Warren's front porch as she passes by on her way to the train station. Knowing that she has gotten back at Marjorie, Bernice laughs gleefully.