A resistor is a mortal with the fortitude to resist being hypnotized by a vampire. Such humans are only a small minority: most people are more or less easy for a vampire to deal with. This has a tendency to lead vampires into complacency—which leads to trouble when they assume that a mortal who has seen them is going to be hypnotizable and they turn out to be resistant to hypnosis. In Hunted, for example, Nick is hunted by a resistor whom he cannot "persuade" to leave him alone.
Any mortal can potentially become a resistor if he or she possesses empirical evidence contradicting the hypnotic suggestion. The ability to resist lasts, however, only as long as the contradictory evidence. If it is destroyed, such a resistor becomes as susceptible as any other mortal. This complication was introduced in Unreality TV, where Nick discovered that it was impossible for him to eliminate the memories of a journalist who had videotaped him flying. Only when the tape was destroyed could she be hypnotized to forget the incident.