Children's Festival DisappearanceEdit
Harriet becomes her uncle's obsession after she disappears on the day of the Children's Festival. He hires a disgraced investigative journalist, Mikael Blomkvist, to try and solve the mystery. The only clues left behind are the last photos of her and her journal with a cryptic entry listing what Henrik and the police believe to be phone numbers. In the novel, Blomkvist's daughter Pernilla provides the answer to the phone numbers. They are not phone numbers but entries in the bible referring to grisly punishments for sinning. Blomkvist and Lisbeth Salander then connect the bible verses to a series of unsolved murders before Harriet's disappearance.
Life in SecretEdit
After solving the mystery, Blomkvist and Salander discover that Harriet is not only alive but living in Australia under Anita Vanger's name. Blomkvist goes to find her and finally learns the whole story. Harriet reveals that her father, Gottfried Vanger sexually abused her and that he taught her brother, Martin, to continue the incest. When she finally had enough she pushed Gottfried into the lake and held him under water with an oar. Martin witnessed his father's death and threatened to expose Harriet as the killer. Luckily, Martin was sent away to school leaving Harriet safe from more abuse. But, when she saw Martin at the parade earlier in the day she is terrified of what he will do to her and she flees with Anita's help.
She borrowed Anita's passport and under her name she married Spencer Cochran and had three children with him. She then lived in Australia, owning a sheep farm with her husband.
Harriet returns to Hedeby with Blokvist after learning of her brother's death. Henrik is overjoyed to see his niece alive. She is slowly brought in as the CEO of the Vanger corporation in place of her brother and takes over Henrik's duties as co-owner of Millenium.