Charles Brady and his recently widowed mother Mary are Sleepwalkers - nomadic, shapeshifting energy vampires who feed off the lifeforce of virgin women. Though they normally maintain a human form, they can transform (partially or fully) into human-sized bipedal werecats (presumably their natural form) at will.

They are considerably more resilient than humans and have powers of both telekinesis and illusion. Their one weakness is cats, who are not only able to see through their illusions.