I'm not a native speaker, so if you're finding some mistakes please feel free to tell me :))
"Cas? Cas, get your feathery ass down here now, we need to talk!"
Dean waited a few seconds before he turned around and found himself only a few inches away from the dark-haired angel who looked at him with his usual sincerely, slightly curious expression.
"Dammit, Cas...I was pretty serious about the personal space stuff, you know?"
The dark-haired nodded slightly, before he stepped away. "My apologies. You called?"
Dean sighted and nodded.
"Yeah...have you ever heard of an angel called Susannah?"
To Deans surprise, the angels face grew pale. "Where did you hear that name?", he asked, a tense tone in his voice.
"Well, Sam and I just finished a job, when we heard about a young woman who got institutionalized by her parents because she kept going on talking about a voice in her head who asked her to be her vessel. We went there and her parents told us that their daughter asked them if she could say yes to the angel and when they panicked and said no... well, in the end their daughter said the same over and over again. Susannah won't hurt me, you don't need to worry. So they decided to seek for some help."
Castiel stayed in silence for a few minutes.
"Where is your brother now, Dean?"
The elder Winchester blinked. This wasn't what he had expected. "He's getting us some food. Why...?"
"Pack your things and call Sam, you need to leave this town."
"Wait what? Cas, what the hell is going on?", he asked and the angel turned around.
"Michael has decided to look for you. And he's serious. Susannah is an angel of his inner circle. Do you know what they call her? Michael's fiercely loyal attack dog. If he wants something to be done, really to be done, he's sending her. And that's why you need to leave. Trust me, you don't want her to be near to Sam."
Dean froze. "What do you mean, what would she do to Sammy?"
The angel sighted. "Susannah would never dare to touch you because Michael needs you. But she knows that your brother is your blind spot. And when she's coming after you, I'm pretty sure she will use Sam to screw out your yes for Michael."
"You don't need to be afraid, Abigail. You're chosen. You're special. And heaven's got a plan for you. An important plan, Abigail. All you need to do is letting me in. Say yes."
"Why me, Susannah?"
"It's in your blood. Lucifer wants to destroy everything. He will slaughter the human race and burn down the planet if Michael won't be able to stop him."
"And … I can help to stop him?"
"Yes. Yes, sweet child. You can help."
"In that case...it's yes. I will help you. I will be your vessel."
Susannah opened her vessel's eyes and stood up.