A myth from the Swedish island of Gotland about the White Sea-Lady has existed ever since Tjelvar, the first man on Gotland, lit a fire and the island rose out of the sea, said to be some 3,000 years ago. The story is told that a young woman who drowned on her wedding night has since tried to lure men down to the deadly underwater currents that tumble off the west coast. The myth of the White Sea-Lady is conjured up one midsummer Gotland island morning, just before a nurse is found murdered in the pavilion on the Tempel Hill of Gorland, in the Botanic garden. She is dressed as a bride. Detective Inspector Maria Wern is investigating the case, but it becomes clear that instead it is the police who are under observation. The killer seems omnipotent, able to taunt and provoke the police with a technical know-how that far exceeds their own. As the killer's demonic plans are being contrived, Inspector Maria Wern realizes the threat that increases with every moment the killer goes undetected.