Disgraced journalist Mikael Blomkvist is hired by industrialist Henrik Vanger to solve the 40-year-old disappearance of his niece Harriet; after Mikael learns he has been hacked by Lisbeth Salander, he hires her to help his investigation.

As Mikael and Lisbeth investigate the disappearance of Harriet Vanger, it turns deadly; Salander discovers a connection between Harriet and a series of murders involving five young women; Mikael and Lisbeth become romantically involved.

Lisbeth is falsely implicated in the murders of her former guardian Bjurman and two of Blomkvist's colleagues; the journalists are working on an exposé of a sex trafficking ring.

Lisbeth avoids Blomkvist, even as he attempts to help her; Mikael continues to try to prove Lisbeth's innocence, while Lisbeth hunts for the leader of the sex trafficking ring; her discovery leads to the last person she would ever expect to see.

A branch of the Secret Police feels threatened by the outcome of the Zala incident; in order to protect themselves, they decide to silence those who may be considered a threat to them, including Lisbeth.

As Lisbeth's trial begins, Mikael races against time to gather information to acquit her; the Section begins a new course of action to stop Mikael's investigation: striking out against Erika and Mikael themselves.