Anita Horrocks is a promising new novelist, able to combine a suspenseful plot with a thoughtful, sometimes poetic, exploration of the concerns and anxieties of teenage readers. Her first novel, Breath of a Ghost, was a finalist in the 1996 Alberta Book Award for Children’s Literature. What They Don’t Know is a compassionate and gripping story of a troubled family. Kelly, the narrator, is disturbed by the changed behaviour of her younger sister, 14-year-old Hannah. Secretive, defiant, and angry, Hannah sneaks out of the house at night through Kelly’s bedroom window, and gets into trouble at school and eventually with the police. The situation is not helped by their new stepmother, who is well intentioned but as unable as Kelly and her father to understand what’s disturbing Hannah.

Horrocks takes an imaginative approach to telling the story: She begins at the end, with Kelly’s reflections on how the events that changed them all started. Set into the text are documents from a box hidden under Hannah’s bed, notes from her friends (and enemies), school and police reports, letters to her father when she was little. The revelations in these bits of paper help the reader build a picture of Hannah, and prepare for Kelly’s discovery of them later. Although the climax is dramatic, it contains too many different crises. A similar overabundance mars the use of symbols in the novel: the striking image of the flight of the nighthawks would work more effectively if it weren’t crowded by too many other pointedly symbolic moments.