Salander proceeds with her decision to act against Bjurman by doing a thorough investigation of him. Unfortunately, her search leads nowhere. Bjurman is a lawyer who has never been censured, a divorcee whose wife has happily settled elsewhere. None of his former trustees ever reported wrongdoing on Bjurman's part. Salander, frustrated with her results, decides Bjurman must disappear.
A shift to Blomkvist finds him getting more and more involved with Cecilia. Blomkvist tries to learn more about Cecilia through his routine conversations with Vanger, learning that she separated from her husband because he was physically abusive and that Vanger sees her as one of the "good" Vangers.
Next, Salander continues to contemplate her options for killing Bjurman in such a way that it could never be traced back to her. Dismissing physical violence, she settles on poison until she realizes that her next guardian could be just as bad, if not worse, than Bjurman. She comes up with a different alternative, although she realizes her plan requires her to meet with Bjurman again.
Returning to Blomkvist, we learn more about his daily routine, and his goal of finishing a draft of Vanger's biography by early fall. He and Vanger meet every evening and both believe that one of the keys to solving the mystery is figuring out the numbers listed in Harriet's diary, even though the mystery seems unsolvable.
Salander arranges her next meeting with Bjurman and is dismayed when he says they'll meet at his apartment. She reluctantly agrees and reformulates her plan to deal with the new setting. Shortly after her arrival, and her attempt to handle the situation, Bjurman attacks her, handcuffing her to the bed and violently raping her. He lets her go early the next morning, reminding her they agreed to meet next week.
Chapter 13 is central to developing Salander's character and raising plot tensions through the trauma she faces. Salander proves to be very thorough in her ability to conduct research, using the Internet as a key source in her investigation of Bjurman's history and in methods to kill him without being implicated. However, Salander's fatal flaw is that, though she can handle information, she isn't good at actually handling people, or reading them. She grossly underestimates Bjurman because she relies exclusively on reports of him, not on reading his body language or dialogue with her. Furthermore, she puts herself in this dangerous situation because she's unable to trust others to help her. This tragic flaw arouses not only sympathy for Salander, but also imbues Chapter 13 with tension. What will Salander do next? Will she finally seek the help of others?
Salander's experience is contrasted with that of Cecilia's history of abuse by her husband, Jerry Karlsson. Vanger suggests that it took a long time for Cecilia to escape the cycle of abuse she found herself in, and only after Karlsson's attacks on her led to hospitalization did she finally leave him. Both women seem to lack a complete understanding of how a violent mind works and how to combat it. In each case, the violence builds to an extreme situation before a resolution occurs. Cecilia's ability to escape foreshadows that Salander, too, may be able to win freedom from her rapist's power over her.