Sarah is Matt’s little sister. It’s unclear exactly how old she is. She’s brave, curious, and self-sufficient, though Matt isn’t willing or able to acknowledge these qualities until he’s been away from Sarah for several months. Indeed, the changing way that Matt thinks and talks about his sister follows his own coming-of-age journey. At first, he doesn’t even mention Sarah by name, but he gradually comes to think of her as a real person. When she finally arrives at the cabin and makes herself busy unpacking, Matt acknowledges that she’s very adult and capable—and someone he’d like to get to know better.