When my brother reached his teens he started having strange things happen to him at night. He would wake up completely paralyzed, unable to move as though an invisible force was holding him down. Sometimes he would hear strange whirring noises too, other times he would feel like his bed was vibrating. He couldn’t speak or call out for help and it used to terrify him. He would struggle and struggle and eventually would break out of it and find himself in his bed, alone and unhurt, with nothing there.