Who is Theo?

Theo is one of the main characters of the novel. In 1985, he is at the wheel when he crashes his mother's car; Misty, the girl riding in the backseat, breaks her neck, and he moves her, not knowing that is bad to do with people who have broken their neck. Even though his sister says she was driving at the time (she has a license and he doesn't), shifting the external guilt to her, he carries all of the guilt of this incident and is unable to even come clean with it.