The current work proposes an evolutionary-based model regarding how genuine forgiveness might emerge on the heels of a betrayal in a relationship between two individuals who co-exist in some broader community. Ancestral human societies were small-scale in nature, usually consisting of no more than 150 individuals. Reciprocal altruism (see Trivers, 1971) evolved as a strong feature of our evolved social psychology in such small-scale contexts. People evolved to develop bonds of trust with others whom they could expect to help them in the future. Under these conditions, breaking trust via betrayal would have had devastating consequences. The current work presents a model for understanding how individuals can get past betrayals given our evolved psychology. The model proposed here includes the four horsemen of the human social-emotional experience, which we construe as a betrayal by the offender, outrage expressed by the victim, guilt expressed by the offender, and, possibly, forgiveness felt and demonstrated by the victim. Based on this model, other responses to the outrage experienced by the victim, such as spite or shame demonstrated by the offender, are unlikely to lead to forgiveness. Thus, this model conceptualizes guilt as fundamental in the process of forgiveness. Implications for modern living and for future research directions are discussed.