Fettes is a weak, selfish young man. He adopts the appearance of a serious student and makes sure to seem polite and studious when his professors are around. Although Fettes maintains a solid reputation as a student, he is selfishly committed to his own desires and interests. He drinks and engages in different forms of immoral behavior but knows to avoid doing anything really dire that could get him in serious trouble. He seeks to benefit from the attention of the popular Mr. K— and does the shady work of intaking bodies and even graverobbing, selfishly profiting from his immoral endeavors. Even when he's faced with the truth of how the bodies are sourced, Fettes shows his weakness by being persuaded by the even more reprehensible Macfarlane to ignore the facts. His deficient character is most clearly emphasized when he not only looks past the obvious murders of Jane and Gray but ultimately congratulates himself on being able to celebrate how he profits from the killing of others.

In the end, Fettes suffers from the conscience he ignores while employed by Mr. K—. With his companions at the George, Fettes is described as a drunk who looks older than his years. His drinking suggests that he attempts to numb himself from some past crises of the soul. It is implied that he never finished medical school because he arrived inexplicably in Debenham while he was still young. Additionally, he is not a practicing doctor but can only perform minimal services in emergency situations, suggesting that he guiltily parted ways with Macfarlane and Mr. K— after the incident with Gray’s body. Abandoning his studies and a potentially lucrative career shows that Fettes is ultimately affected by his conscience and plagued by guilt in the subsequent years.