On holiday with their mother in the Lake District in 1929 four children are allowed to sail over to the nearby island in their boat Swallow and set up camp for a few days. They soon realise this has been the territory of two other girls who sail the Amazon, and the scene is set for serious rivalry.

Janet is a young student at a private school; her nights are troubled by horrible dreams in which she sees her mother, who is in fact locked in an insane asylum, haunting her. Expelled because of her persistent nightmares, Janet is sent home where the nightmares continue.

A young man murders women, using a movie camera to film their dying expressions of terror.