A former student of orangutan pacifist Mandemus, Virgil went on to become Ape City's resident scientist and theoretical thinker, and an advisor and friend of Caesar. Apes and humans are both among his students, and he feels sorry for the humans' second-class status in Ape City.
Caesar calls Virgil away from his teaching work, to accompany him and Mr. MacDonald on a trip back to the Forbidden City, to search for recordings of his parents Cornelius and Zira, and information about Earth's future. Carrying a Geiger counter into the Forbidden City, Virgil warns Caesar plainly about the radioactivity and accompanying dangers. (He also authorizes MacDonald to bring a pistol, in case he may "wish to shoot, cook, and eat a rabbit" during the trip; something humans were normally not allowed to do.)
Returning from the Forbidden City (after barely escaping with their lives, from mutated human survivors who stayed underground), Caesar and Virgil reluctantly prepare Ape City for a possible attack. General Aldo, called to action, sees the chance to take power instead. When Caesar's son Cornelius is gravely injured in a fall from a tree, MacDonald discovers the ends of the broken branch, determining they were cut, and he and Virgil deduce Aldo was the culprit.
Virgil fights and leads apes when the mutant humans do attack, calling Caesar out to take charge. After the battle, he is the one who must tell Caesar that Cornelius was murdered by Aldo. Later, he helps to rebuild Ape City, with its new status of apes and humans as equals.