The episode starts out with Sam getting a text of some coordinates. Turns out it's for Bristol, RI and there are some missing girls there. So with some reluctance from Dean, they decide to go. Turns out Sam and Samuel were there a year before and some people died in the hands of Sam and he beat up a cop. Of course Sam doesn't quite remember all that but he does get deja vu when they get into town. They figure out it's something called Arachne and that all the women taken were ones that Sam slept with. Sam checks out things with police and the officer that he beat up puts him in jail. Dean talks to the missing person's roommate and sees a business card that was Sam's. While Sam is in jail the sheriff's (he died a year ago) wife talks to him. Apparently him and Samuel told the sheriff and his wife the truth that they are hunters and that way they would help them. He convinces her to let him out so he can catch this thing.
We find out through a flashback that Sam and Samuel used the Sheriff as bait to catch Arachne. They follow her to an abandoned warehouse where several men are uncased in webs and Sam decapitates Arachne. He then tells Samuel that the men will die anyways and so he puts them out of their misery, including the Sheriff and shoots them all. Then he burns the warehouse down. And that's the end of that but not really.
Turns out the men that were in the webs were not poisoned but turned into arachne and one of them is the Sheriff and he's out to get Sam. They fight and the wife is there and finds out what Sam did. All ends well, except at the end Sam collapses in a seizure of some sort. We see him burning in hell in the cage. Looks like the wall has come down.