The boys came up against yet another villain from the Book of Revelations, the Whore of Babylon. Claiming to be a prophet, she had an entire town under her sway, and was trying to bring them all to Hell. Using promises of being reunited with dead kin and being saved come judgement day, she convinced good people to commit unspeakable acts from which none could be saved. Too bad for her that Dean (Jensen Ackles) and Sam (Jared Padalecki) happened to pass through her town.
I'm going to say this once, and just once, "Why are all these things happening in the USA." I realize that Sam and Dean are there, and we have established that they are a huge part of the Apocalypse and the Fates do love them, but are there no demonic activities in Europe or Africa or anywhere else? Or are we just suppose to assume that before the Whore came to that small American town, she was doing the same thing somewhere in China? That Death and War and Famine and Pestilence are doing their things in Australia and Argentina? What explanation have you given yourself for why all this turmoil is centred on the States?
Ignoring that, Sam and Dean would be completely screwed without Castiel (Misha Collins). Showing up, eventually, in response to a call for help (left on an answering message with a very amusing recording), Cas reveals that Leah (Kayla Mae Maloney) is not a prophet, and must be the Whore. He is quite wrecked at the time, explaining that he found a liquor store, and drank it. Poor Cas, there is not enough liquor in the world to drown an Angel's spirits because his dad is a dead-beat like most other people's.
Cas also revealed that only a true servant of God could kill the Whore. Luckily, there was a priest on hand, but as he was the girl's father (before she was killed and the whore took her shape), he hesitated, and Dean ended up impaling the creature. To everyone's surprise, she died. Apparently Dean is a true servant.
And what did Dean do upon discovering this? He ran (well, drove) away from his brother. He showed up to see Lisa, the love of his life, to tell her that he loved her and to promise her than one of his conditions for the thing he was about to do (likely saying YES to Michael) was that she and her son would be protected and saved.
The big show down is coming, how it is going to happen, how we are all going to survive long enough for season 6, I cannot say. But I am certain that it will not only be epic, but the transition will also be credible. This show continues to be amazing 5 seasons in, and I have every hope season 6 will also deliver.