heh, sounds like the Negapsychic class in Palladium's old Beyond the Supernatural RPG. Their disbelief in the paranormal is so strong that their inherent psychic powers tun into a jamming field of sorts, shutting down nearby magic and psionics.
So there's parts of Brockton Bay that the Capes all avoid (hero and villain) because something shuts down their powers in that region. Their pretty sure it's a parahuman, cause it does move around, but whoever it is is (naturally) immune to Thinkers, and whoever it is doesn't run around in a costume (at least no new Capes have been reported. Do they even know they have powers?)
So there's parts of Brockton Bay that the Capes all avoid (hero and villain) because something shuts down their powers in that region. Their pretty sure it's a parahuman, cause it does move around, but whoever it is is (naturally) immune to Thinkers, and whoever it is doesn't run around in a costume (at least no new Capes have been reported. Do they even know they have powers?)