Neville immediately assumes that the dog is trying to hide from the vampires outside, but it seems just as likely that the dog is trying to escape from Neville, the last uninfected man on Earth! Notice also that Matheson doesn’t say what happens when the dog “dies.” Given that vampires die and then wake from the dead, it’s probable that Neville burns the dog in the pit to ensure that it won’t rise from the grave. Neville, continuing to think of himself as the “good guy,” fails to see things from the point of view of the infected—he thinks he can “cure” vampires, when, in the end, he just ends up burning them to ensure his own survival.