Dean is packing some bullets with the ash and says it doesn't hurt him and so how could it hurt Eve. They have to figure out how to get her and ask Castiel to help find her. They get the idea to find a monster that is against her and Castiel goes and gets Lenora. She was a few seasons back as a vampire that was living off animal blood. She told them where Eve is and asks for them to kill her. Castiel does the job when the boys can't.
So they go to Grant Pass, Oregon where she has been infecting people with something that is killing them. They finally go to Eve at a diner where she's a waitress and a room full of hybrids. The perfect monster as she calls them and all the people that were dying were betas. She finally got it right. She said that she was happy with the arrangement she had and that it all changed when Crowley started taking her monsters and even first borns and killing them. She says that Crowley is still alive and she will leave and not hurt the boys and friends/family if they work for her in eliminating Crowley. Dean gets her to bite him and he's drank the Phoenix Ash and she dies.
The world is saved but now they wonder if Crowley is dead or alive and Castiel says he'll look into it. Then we see him and Crowley talking and Crowley saying he's cleaning up his messes again. So looks like Castiel is keeping Crowley around for some reason.