С 1, с 1: Puck Ekstedt has been invited by her university tutor to celebrate midsummer at his summer house on a secluded island, together with a group of friends including Einar Bure. Puck and Einar (Eje for short) are secretly courting and he is the reason she accepts the invitation. The summer nights are seductively beautiful until Puck finds one of the female guests murdered. Einar contacts his best friend Christer Wijk, a police inspector, to investigate. In the meantime, they are trapped on the island - and someone amongst them is a killer.