There are stories about a certain kind of hitchhiker - they only ever appear at night on quiet roads, seeming to flicker into existence in the very edge of headlights, never carrying a sign, always with an expression of deep despondency on their faces, swathed in a heavy coat and long pants, usually with gloves. If you stop, they will seem cordial enough, polite, but hardly chatty. They will assure you that the next town or city along your route will be a fine spot to leave them. Normal enough. Unless you try killing them.