Early in the morning, Salander sneaks over to Martin's and investigates his secret torture room. She finds binders and videotapes documenting the women he has brought there, many of whom were recent immigrants and unmarried, thus their disappearances aroused little to no suspicion. Salander also finds two faded Polaroid pictures, which she pockets. The rest of the material she burns in Martin's woodstove.
That afternoon, Blomkvist and Salander go over the facts and recognize a young Harriet in the Polaroids Salander saved. They begin to realize that Harriet was being sexually assaulted by both Gottfried and Martin. Martin's unexpected arrival in Hedestad the day of the parade is what prompted Harriet's desire to speak with Henrik. Realizing their next move, Salander and Blomkvist pack their bags and head out of town.
The twosome flies to London where Anita Vanger lives. But before paying her a visit, they have one of Salander's hacker friends tap Anita's phones. Blomkvist visits with Anita and confronts her about Harriet, saying he knows she helped Harriet disappear that fateful day. Anita kicks him out of the house then promptly makes a phone call to the long-hidden Harriet, who's currently living in Australia. Having tracked down Harriet, Salander and Blomkvist book flights to Australia. Before they leave, Armansky calls Salander to tell her that her mother has died. Salander returns to Sweden instead, leaving Blomkvist to travel to Australia alone.
Chapter 25 introduces the theme of nature versus nurture and provides a shift in emotional tone. The nature versus nurture theme emerges as Blomkvist and Salander try to piece together the missing parts of the puzzle revolving around Harriet and her father and brother. Blomkvist suggests that Martin had little choice in becoming who he was, because of his father's influence and abuse. Salander argues that it is irresponsible to excuse the creeps in the world for bad behavior blamed on how they were brought up. The discussion supplies insight into Blomkvist's and Salander's characters. Blomkvist sees himself and other humans as part of a social fabric, subject to various influences that shape their free will. Salander, on the other hand, uses her own life as evidence that a person, no matter the difficulties encountered, is responsible ultimately for his or her own choices, be they good or bad.
In this chapter, the sense of doom diminishes and hope returns. This promising tone is especially felt in the scene where Blomkvist and Salander successfully track down Harriet. They find out that Harriet successfully escaped from her evil father and brother. She survived and is living in Australia, which makes the flower present in the prologue — Desert Snow, a native to Australia — all the more fitting. Her survival is particularly significant in its relation to the exploration of violence throughout the novel. Like Salander, Harriet refuses to accept having an attacker in her life. Unlike Salander, however, Harriet is able to seek help from others.