Commentary Inf XVII 97-99

Virgil's commands to Geryon, coupled with the monster's instantaneous disappearance once his tour of duty is ended, make the reader realize that Virgil has used extraordinarily persuasive arguments to tame this beast. His having sent Dante away also reminds us of the time he left his charge alone but in sight of his temporary yet crushing defeat at the hands of the demons at the walls of Dis. This time he first gets his pupil out of viewing range and then, we do not know how, manages to control a most difficult demon and turn him into the first helicopter. If Dante is the main learner in Inferno, Virgil learns a few things himself.