1x06 The Case of the Creeping Forest

@tedford People who have near-death experiences, have supernatural abilities or supernatural experiences can see ghosts. Even without her powers, Crystal has had plenty of experiences with the supernatural by this point, and there are other reasons that we find out in this episode as to why she can still see them.

@justgeekingby With that logic more than half the human population should be seeing ghosts

@tedford They probably do, but not everyone is receptive to the idea and automatically ignores them or thinks they are alive.