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In 1966, sixteen-year-old Harriet Vanger vanished from Hedeby Island while a traffic accident had blocked the only bridge, so her great-uncle Henrik spent decades treating it as a locked-room murder by a family member. Blomkvist and Salander found that her brother Martin, taught by their father Gottfried, was a serial rapist and murderer of women.
The state declares Lisbeth Salander legally incompetent, and that status hands total control of her money and life to her court-appointed guardian, Nils Bjurman. He uses that control to extort and rape her, knowing no one will believe a ward of the state with a psychiatric file. The legal system built to protect vulnerable people concentrates power in one unsupervised person, and that power becomes a tool for abuse.
Martin Vanger and the corrupt financier Wennerström both commit serious crimes for decades because their wealth, status and family name make others slow to suspect them or quick to protect them. Blomkvist's libel conviction shows that the powerful can use courts and press relationships to punish whoever exposes them. Social standing works as a shield because institutions give credibility to the powerful and deny it to their accusers.