Blomkvist is totally surprised. He hadn't heard anything about a murdered Vanger.
Saturday, September 24, 1966. The Vanger family is at Hedeby Island for the annual dinner.
Harriet attends the Children's Day parade in Hedestad, and gets home at around 2pm.
At 2:15, a tanker truck turns over on the bridge connecting Hedeby Island with the mainland.
For the next 24 hours, nobody can get on or off the island, other than rescue crews in a boat.
Blomkvist correctly guesses that something happened to Harriet during that time.
The 64 people on the island at the time are all suspects.
Harriet is last seen by Otto Falk, Hedeby's pastor, around 3pm.
Blomkvist learns that the cause of Harriet's death remains unknown – because no body's been found.
Henrik is sure it's murder because: a) even if she'd left the island, she couldn't have survived on her own at sixteen, and then managed to hide for 36 years; b) if she'd killed herself, or had an accident, they would have found a body.
Somebody must have killed her, not drawing blood, and then driven the body away the next day.
Salander spends the morning reading Blomkvist's controversial book on blasting unethical financial journalists. She admires his jacket photo.