Salander, sleepy from a long night at a bar and a sexual encounter with her on-again-off-again female lover, is shocked when someone rings her doorbell. She's even more shocked when Mikael Blomkvist stands before her, offering her a bagel and a job. After Salander recovers from her initial panic, Blomkvist explains that he wants her to research the women Harriet pairs with the Bible verses. Salander, after hearing his story, quickly agrees to help him.
While in Stockholm, Blomkvist heads over to Millennium's offices to surprise the staff. Berger's happy to see him and lets him know everything is going smoothly — except with one of their most recent hires, Janne Dahlmann. Both Berger and Blomkvist realize that hiring Dahlmann near the start of the Wennerstrom affair was a mistake, but now Berger suspects Dahlmann is not really on their side — that he may be working for someone else. Blomkvist urges her to trust her instinct and fire Dahlmann if she has to.
Upon returning to Hedeby, Blomkvist immediately senses that someone has broken into his cottage and rifled through his research. He decides to order a new deadbolt. He then visits with Frode to hear about Vanger's condition, which is stabilizing, but still serious. Later that night, unable to sleep, Blomkvist thinks about Salander and what an odd girl she is.
The theme of trust is pivotal in Chapter 18 as a variety of characters try to grapple with new situations. First, trust is a major issue for Salander and Blomkvist, as this is the first time they meet. Blomkvist, known for being a lady's man, is baffled by this woman who seems removed from his charms. Salander, who doesn't invite many people over to her home, let alone strangers, is surprised by how quickly she feels comfortable with Blomkvist. That the two of them seem immediately in sync — as highlighted by Armansky's jealousy when watching them work together at Milton Security — indicates that trust isn't logical but instinctual. Trust is less initiated by actions than by feelings, and Salander and Blomkvist immediately feel safe with each other.
Trust is also an issue for Millennium as Berger shares her fears about Dahlmann with Blomkvist. Blomkvist and Berger have an instinctual gut feeling about Dahlmann even though they can't point to a specific thing he's done to inspire it. Berger's suggestion that Dahlmann is working for someone else also foreshadows more problems to come. Is Dahlmann a double agent for Wennerstrom, or some other entity? Berger's decision to not fire Dahlmann based solely on her unproven suspicions suggests that she may regret her caution in the long run.
Finally, trust is also an issue for Blomkvist when he returns to Hedeby to find that his home's been broken into. While he's mostly shared Vanger's opinion of the rest of the Vanger clan, he hasn't been directly affected by the family's more negative members. Despite some heated exchanges with characters such as Isabella and Harald, the family has kept its distance from Blomkvist. Now, Blomkvist knows that someone's nervous about his research, suggesting he's closer to the answer than he knows. He also must, now that Vanger is in the hospital, rely on his own instincts to decide which Vangers to trust.