Henrik Vanger notes Blomkvist's interest in Harriet's story and proceeds to relate the specifics regarding the day of her death. The Vanger clan had gathered at his house to talk business one summer day. Mid-afternoon, a horrible car accident blocked the bridge to Hedeby Island, causing chaos for a few hours as people on the Hedeby Island and Hedestad sides of the bridge attempted to save the drivers. Although Harriet was seen during the commotion, she had vanished by the time things settled down. Vanger insists that the only plausible explanation for her disappearance is that she was murdered and the killer skillfully got rid of the body. A search of the whole island and the waters around it never produced a sign of Harriet.
Next, the scene shifts to Salander, returning to Christmas morning. On that morning, Salander read Blomkvist's book, The Knights of Templar: A Cautionary Tale for Financial Reporters. In her reading, she learns more about Blomkvist's disappointment with his fellow reporters. Salander begins to understand why Blomkvist got so much negative press during the trial — he had made plenty of enemies through the stories he had written and the reporters he had ridiculed. During the early afternoon, Salander sends a cryptic message to the e-mail address firstname.lastname@example.org before setting off to do reconnaissance on Wennerstrom's apartment building. She easily sneaks into the building, photographs the electrical box in the basement, and scoots out without arousing any suspicion. Upon returning home, Salander receives an equally cryptic response to her cryptic question from plague_xyz_666.
Chapter 5 not only presents a fascinating description of the day Harriet vanished, but also provides significant insight into Salander's character through both description and allusion. First, Stieg Larsson foreshadows several important clues to Harriet's mysterious disappearance. For example, on the day of her murder, Harriet urgently wanted to tell both Vanger and the local pastor something. Both men, distracted by other business, did not give her the time to talk to them. Whatever she wanted to say might be a clue to the fate she met that day. Furthermore, Blomkvist seems unconvinced that murder is the only explanation possible for Harriet's disappearance, as he asks several questions to determine if she somehow escaped the island without notice. While Vanger dismisses the suggestion that any cause besides foul play would be implausible, the lack of a body still supports a chance that Harriet may have left the island that day. Vanger and Blomkvist's dialogue shows Blomkvist's reporter mind hard at work, trying to see through Vanger's story to put together a more complete truth.
Salander and her abilities become clear in Chapter 5. Although Armansky sees her as someone unwilling or unable to conform to social norms, Salander is able to subtly manipulate her appearance in order to further an investigation. Before setting off to Wennerstrom's apartment building, she removes her piercings, puts on plain lipstick and simple clothes to create a more innocent, nondescript appearance. Her ruse works because she is able to nonchalantly see the entrance code to the building when a tenant arrives and finds her presence at the building door nonthreatening. This smooth and effortless ability to use her resources to find out information seems to be Salander's key strength. Her cleverness helps explain why the young woman seems so distant to Armansky and others: She clearly sees herself as more competent than others and not in need of much assistance.
Finally, Larsson includes an allusion in Chapter 5 to provide further foreshadowing to Salander's character development. Salander writes to an e-mail address called "plague_xyz_666." All three elements in that address are indicative of something apocalyptic: first, reference the Bubonic Plague, the scourge that wiped out much of Europe's population in the late Middle Ages, followed by the last three letters of the alphabet, also indicative of the idea of the end or death. The number "666" refers to the devil, or the Christian Bible-based antichrist, finishing off an e-mail address that elicits a sense of doom and prophecy. That Salander is communicating with someone with such an e-mail address indicates that she may have a more complex personal life than she's comfortable discussing.