Readers should remember that Gus asked two things of Call before he died: first, that Call take him back to Texas. And then, equally importantly, that Call acknowledge Newt and take on the role of the boy’s father, a role that rightfully belongs to him. One of these is easier for Call. Unfortunately, it's also the less important one, because it’s the promise made to a friend who is now dead and unable to care whether it’s completed or not. In the end, his pride proves stronger than love. And this surprising twist, this unclosed loop becomes the book’s biggest tragedy.