Horror Master Richard Matheson poses a complex and searing question in what is arguably one of the greatest and most ironic vampire tales of all time: just who is the real monster here? Despite the fact that Neville is the last known human survivor on earth, he is troubled by his own masculine sexual repression and an unexplainable need to kill as many vampires as he can by day, although the resulting effects are fruitless in a world where he is now the pervasive alien force. Through his isolated days of contemplation, Neville reflects on the misdeeds of the human race and contemplates his reasoning for his senseless killing.
Neville underestimates the process of evolution; in the three and a half years of his existence in the apocalyptic world, the vampires begin to advance and form an organized society, eliminating those that refuse to succumb to their purpose. This movement remains unknown to Neville until a female spy, looking and acting more human than Neville himself, infiltrates his stronghold and attempts to connect with him. Neville remains distrustful and she eventually flees his stronghold, warning of a plan against him and his kind. She also explains that the vampires have developed a pill that enables them to resist the temptation to feed. While they have managed to replace their base instincts of vampirism with an efficient violence, Neville can no longer clearly justify his own murderous actions. In a moment of extreme self-discovered irony (I’ll not spoil the ending for those being exposed to Matheson’s work for the first time), Neville comments on his observed violence of the new society of vampires, to which Ruth, the female vampire spy who tried to warn him away, cites the need for species survival as an appropriate justification for atrocious actions. She uses the horrific history of human society as a prime example of this concept and argues that the “revolutionary” idea of creating a new society through violence is nothing new; the vampires are replacing a violent society founded on bloodshed and other acts of war. I Am Legend indicates that the old society, and Neville, who once belonged to it, have no place in the new order of existence. Neville is now the fabled monster in a foreign world, a relentless and ancient killer who stalks the vampires by day and becomes the source of an unthinkable evil in his obsolete humanity.