In Chapter Fifteen, the theme of the natural versus the unnatural emerges in the metaphor that is used to describe the differences between Bruno's and Shmuel's hands: "[although] Bruno was small for his age, and certainly not fat, his hand appeared healthy and full of life. The veins weren't visible through the skin, the fingers weren't little more than dying twigs" (168). Shmuel's living situation at Out-With is unnatural and thus, like a withering tree, he is slowly dying. The difference in the boys' hands is presented as a physical representation of just how different their life experiences are at Out-With. Shmuel tells Bruno that "[everyone] on my side of the fence looks like this now" (168).