The book deals with the theory that time is relative, and can be fluid and unstructured. In one respect it can be viewed as a time travelling story. At the very core of the novel is the "child in time" — Stephen himself — appearing to his mother as a child's face at a window, which makes his mother decide not to abort, but instead to continue the pregnancy.
It also explores the way both Stephen's and Julie's lives disintegrate after Kate's disappearance, and how an unexpected event at the very end of the book may bring them back together.
