It's about a girl (hacker,somehow with punk/gothic look, also abused that maybe the reason) and a journalist who later worked together in a case. I guess they fell in love on the last film. :P
Lisbeth Salander is a 23-year old hacker, working as a private investigator for the security firm Milton Security. She is under legal guardianship due to her history of violence and being held in a childrens' mental institution. Despite her small size, she can fight like a man. She has photographic memory and the nonexistent social skills of someone with Asperger's syndrome. However, it is never actually stated that she does have Asperger's or anything of the kind, only that she is a very troubled, antisocial woman who is nonetheless capable of great compassion and loyalty.
Michael Nyqvist (Mikael Blomkvist)
According to the author, "Mikael Blomkvist is a graduate of the School of Journalism and had much of his professional life dedicated to revealing and report suspicious transactions, specifically in the field of banking and business," writes Larsson in the first volume of the trilogy. "It will give the typical image of guardian of the moral, incorruptible, facing the business world. And as such quite frequently invite you to comment on various issues in television."
Source: IMDB & Wikipedia.