Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
First Person (Central) and Third Person (Limited Omniscient)
Where Things Come Back is a special book because it employs not one, but two narrative techniques. Fancy, right?
First Person (Central Narrator)
When we get Cullen's side of the story, it's definitely told from his own perspective. We get his voice, insight into his thoughts and obsessions, and the emotions that no one else gets to see when his brother goes missing. On the outside, he may seem stoic and unfeeling, but because we're hearing the story from his perspective, we know that he is deeply affected by Gabriel's disappearance and just wants his brother back.
Third Person (Limited Omniscient)
When the book switches to the Benton/Cabot/Alma storyline, though, it goes to the third person perspective, with limited omniscience. This means that we get the story as told from the perspective of a non-involved narrator, but we get to see the thoughts and inner workings of each character that said mystery narrator is focusing on.
For example, when the chapter is focused on Benton, we see his confusion over being a missionary and whether or not he's doing anything of worth for the Lord. And when Cabot is the focus, we get a glimpse into his mind as he becomes increasingly religious and fanatical.
When the narration styles combine, we get a pretty thorough understanding of a variety of characters, so when everything collides and the various plot threads finally come together, we see the big picture super clearly.