Instead, they use the haunted house story to set up a series of ghostly tropes. They want to explore how the situations feel from both sides of the veil and how difficult it is to communicate between worlds. Dean taking a shower while Bobby writes on the mirror is a very recognizable horror scene, but we don’t usually get to see the ghost’s frustration at having to work so hard to communicate. Bobby and Annie looking out the window of the haunted mansion as Sam and Dean drive away is another horror story standard—except this time we see how frustrated Bobby is at being tied to the flask. Even when we get a pretty standard Sam and Dean ghost fight, we have the added layer of the danger to Bobby’s spirit—and that is what lies at the heart of this story.
When Sam and Dean return to the haunted house, they can finally see Bobby. His power as a spirit has grown as he learns how to crack the code of living as a ghost, so in this place where the spirit and living worlds touch, he breaks through. The three men figure out why they couldn’t communicate earlier (Sam tried the talking board when Dean had the flask elsewhere), but Dean has more he wants Bobby to hear.
To Bobby’s surprise, given how grief-stricken Dean has been, the elder Winchester isn’t overjoyed to see him. Dean asks Bobby what happened to prevent him from moving on. Bobby testily replies, “I wanted to stay. I need to help.” Needing to help is the Winchester way, so he is surprised Dean is upset Bobby has stuck himself as a ghost. Rather hurt, he says to Dean, “Stuck here with you?” He’s prepared to stand by his adopted sons and battle the Leviathan with them. What could be wrong with that?
Dean, however, is looking at a different future. He tells Bobby, “It’s not right, you know that.” It’s against the natural order, and Dean had a good schooling from Death last season on not interfering with the natural order. But Dean himself and Sam are living examples of going against the natural order, so it would be surprising if Dean couldn’t get past that. The real problem for Dean is revealed by his last words in the episode: “What are the odds this all ends well?”