The major protagonist of the novel, Mikael Blomkvist is the publisher of the political magazine Millennium and an investigative journalist in his fifties. When a libel conviction throws his credibility into question, he accepts an unusual freelance job from Henrik Vanger in an effort to think about his uncertain future and, hopefully, to clear his name. A man of integrity and scrupulous ethics, Blomkvist initially has a reputation as a watchdog reporter willing to expose corruption. As the emblem of investigative journalism, he thusly becomes the material of much disparagement and mockery after his conviction. Since his value as a reporter lies in his credibility and Millennium rises or falls with Blomkvist’s reputation, the novel is in many ways the story of Blomkvist’s quest to restore his good name. Even his association with the Vangers underscores his honor since he remains true to his word and solves the case at great risk to his life. Unfortunately, throughout the novel Blomkvist also learns that the effort to restore his credibility will depend, at times, on less than ethical means.

Despite his integrity, Blomkvist’s personal relationships suffer from his inability, or unwillingness, to commit to serious relationships. While Erika Berger remains his longest and most serious relationship, he seems to find relief that she, long-married, does not seek a permanent home and family with him and spends time with other lovers during his time in Hedeby. He has a cordial if distant relationship with his ex-wife, but his most vibrant and passionate relationship is with Lisbeth Salander, his ally in solving the disappearance of Harriet Vanger. Blomkvist willingly accepts Salander’s various quirks and her emotional restraint, and he respects her intelligence and abilities. Even so, he doesn’t become emotionally attached to Salander as she does to him, and though Salander is the one who seems initially cold, by the end of the novel it is Blomkvist who appears to have the greatest problem with intimacy. Salander does change him in one significant way, however. At the start of the story, Blomkvist possesses a strong earnestness and a naïve, frequently idealistic sense of the world that sometimes neuters his ability to solve problems or deal with them efficiently. But after his time with Salander, Blomkvist becomes comfortable using less-than-ethical means at times to accomplish his goals and strike back at those who would damage his reputation.