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.

Charles and Mary have taken up residence in a small Indiana town called Travis, having recently fled Bodega Bay, California (where they used the aliases Martha Brodie and Carl Brodie).