The storyline for this episode is weak and not worked well upon. Sam and Dean, thanks to the writers who have depended on co-incidental rather than an intelligent mystery-solving story, get lucky throughout the story and use none of their daemon-hunting skills that the show is all about. The way the two get from one step to another on their way to unveil the mystery is totally uninteresting. Replace Sam and Dean with me and my accountant brother and still the episode would be believable. What's more, no imagination has been put in creating the evil spirit here. It's not just unoriginal but badly adapted from whichever of the numerous sources it has been taken from.
All in all, just an episode to fill the spot.