What is Siobhan's role in the novel?

Siobhan - Christopher’s primary teacher at school. An even-handed mentor, she works to expand Christopher’s horizons socially as well as academically. As a result, she is one of the few people whom Christopher trusts, and in the limited moments when the reader sees her, she mirrors the reader as an observer and commentator on Christopher’s life.

Siobhan, meanwhile, plays the role of quiet observer, working much as the reader does to understand Christopher better through his novel. Siobhan initially tells Christopher to write his novel to give him a simple writing exercise, but the book’s autobiographical nature soon reveals Christopher’s inner thoughts and home life to Siobhan. In Chapter 109, Siobhan reads of Mother’s affair with Mr. Shears, and she realizes that she has inadvertently learned a secret about Christopher’s family. She attempts to engage Christopher in a discussion of his feelings about the affair, but Christopher reveals very little about his emotional reaction, just as he tells the reader little about his feelings on the subject. He instead dismisses the matter with logic, saying it makes no sense to worry about the affair when Mother is dead and Mr. Shears is gone. Because of Christopher’s condition, which leaves him socially and emotionally impaired, this response may in fact reflect his true feelings. But this virtual non-reaction leaves Siobhan, and perhaps the reader, to wonder exactly how Christopher experiences the world.