Oliver is the narrator of the novel and its main protagonist. Diffident and unassuming, Oliver discounts his talents and his physical attributes. He believes luck, rather than skill, has allowed him to survive the annual cuts at the Dellecher. His modesty prevents him from seeing what is obvious to his peers, namely that he is a generous actor and person, who allows others to shine. He is also baffled why Meredith finds him attractive, even though Filippa makes it clear that he has much to offer. Often cast in the role as a sidekick, Oliver is a protagonist who believes he does not belong in the spotlight. 

As the novel progresses, Oliver matures and, as he does, develops a notable capacity to accept responsibility. For example, when the group discovers Richard’s body, Oliver volunteers to wade into the water to see if he has died. Although he is terrified, he subordinates his feelings to the needs of the group, a trait he repeats with frequency across the novel. Although he suffers under the oppression of grief, which he represents as a monster, he seeks ways to lift the burdens from his friends. In an act of extreme generosity, he even confesses to a murder he did not commit so as to protect his friend, James, from prison. If We Were Villains is, in many ways, a coming-of-age novel and the character who shines in this capacity is its narrator, Oliver Marks. 

There is one further way in which Oliver’s character evolves across the novel. As roommates, James and Oliver are close but, as the action unfolds, they come to recognize that their feelings extend beyond friendship. Although they are attracted to women—Oliver to Meredith and James to Wren—their intimacy is increasingly powerful and eventually leads Oliver to choose between Meredith and James. With his confession, he picks James, a choice he had made previously in the novel and seems to be repeating at its close as he researches James’s death.