Theory of mind is the understanding that other people have mental states that drive their actions and that those mental states can be different from one's own. Without understanding theory of mind and being able to take others' perspectives, it could be difficult for children to read and understand narrative texts. This paper posits that children's understanding of others' minds may be a potential missing piece in current accounts of reading comprehension. Indeed, the typical progression of children's theory of mind abilities across childhood is closely aligned with the development of narrative processing skills. Furthermore, emerging evidence shows that both narrative processing and theory of mind are predictive of children's reading comprehension, both concurrently and longitudinally. We present a possible explanation for why such a link exists and propose a causal framework of this relation in which increased ToM leads to increased understanding of and inferencing about characters' mental states. Understanding characters' mental states then leads to better reading comprehension. The framework makes novel, testable predictions and provides directions for future research.