This episode is all about Dean. Ben & Lisa are kidnapped and he gets an urgent call from Ben. It is Crowley that has taken them both. So Dean sets out to find them and bring them back. Castiel didn't know about this and is mad at Crowley.
Also we have a flashback to H.P. Lovecraft and how him and his friends opened up a portal to Purgatory and let something in. That something killed him and his friends and that something is that professor that had the Dragon slaying sword. Bobby finds her in one of her hiding places and tell her that Castiel & Crowley will come looking for her and find her. She doesn't want to go back to Purgatory because she likes Earth. Turns out Castiel find her and takes her.
Dean is able to find Ben & Lissa with Balthazar's help and he rescues them. But Lisa is possessed and stabs herself and he brings her to the hospital. Castiel shows up and tells Dean he's sorry. He cures Lisa and Dean asks for one favor. So Ben and Lisa forget all about Dean.