Holly meets the narrator by climbing into his bedroom window one night.
Holly throws loud and raucous parties, usually attended by lots of men. She invites the narrator to one of these parties and this is when we learn about her time in Hollywood from O.J. Berman.
We also learn of her regular visits to Sally Tomato in Sing Sing prison. She does it for the money but also because she really likes the man.
Holly and the narrator get into a wicked argument and avoid each other in the halls of the apartment building after the fight. But then Doc Golightly shows up to reclaim his wife, and this prompts her reconciliation with the narrator.
Holly and Doc have a happy reunion and we find out that they sleep together. But she doesn't return to Texas with him and instead stays in New York.
Holly, Rusty, Mag, and José go on a trip to Florida, during which Holly and José start having an affair. After they return, Holly finds out that Fred has been killed in action and she has a complete breakdown and destroys everything in her apartment. She never talks about Fred again.
After Fred's death, Holly throws herself into domestic life with José and we find out that she's going to have a baby. Eventually, José proposes to Holly and she plans to go to Brazil with him.
On one of her last days in New York, Holly invites the narrator to go horseback riding in Central Park. He almost gets into a terrible accident with his horse and Holly races to help him, and she's able to help stop his out-of-control horse.
Later that evening, Holly gets arrested for her role in the drug ring run by Sally Tomato. She ends up in the hospital because she lost the baby after the horse fiasco with the narrator. While she's in the hospital, she learns José has left her in order to avoid being associated with the scandal.
She decides she's still going to go to Brazil since her ticket is already paid for, and she succeeds in leaving the country without being caught by authorities. The narrator doesn't hear from her for months, but she finally sends him a postcard from Buenos Aires. We learn that she has fallen in love with a married man and that she hasn't found a place to settle since she can't live with this guy. She promises to write to the narrator when she's more settled, but he never hears from her again and we're left to wonder what happens to Holly at the end of the novel.