Who is Henrik Vanger from The Girl with the Dragon Tattoo and what is their importance?

Henrik Vanger is an 82-year-old industrialist and head of the larger and dysfunctional Vanger family. He is obsessed with the disappearance and apparent murder of his great-niece Harriet more than 40 years earlier, and he hires journalist Mikael Blomkvist to solve the mystery under the guise of writing a chronicle of the Vanger family.