The 16-year old girl Harriet Vanger disappeared without a trace, on September 29th 1966. Nearly forty years later a journalist by the name of Mikael Blomqvist gets an unusual assignment. He is contacted by the industrial leader Henrik Vanger, who wants him to write the history of the Vanger family. The family chronicle is just a cover for the real assignment: to find out about what really happened to Harriet.