Ghosts are NPC found in Robbery Bob 2: Double Trouble, the Hauntington Chapter. When they see Bob, they'll chase him without getting tired unlike cops. Ghost are quite different from aliens as aliens teleport through close door while the ghost can pass through any walls or doors, making the ghost the hardest NPC found. However, If you stick to a wall then move or stand still where you are, the ghost won't chase you even you're in it's sight. Ghosts can be eliminated by ghost traps, one per time.
When a ghost approaches into a ghost trap, it will be eliminated. Ghost traps are connected to a wire, providing power from the ghost to open doors.