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 were working on an expose 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. Now, 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, but "The Section" begins a new course of action to stop Mikael's investigation: striking out against Erika and Mikael themselves.