We're on a train. Sherlock was sitting in a section by himself. He wanted to think alone. He sat there laid back in his seat, eye closed, hands folded on his lap, in his mind palace. Sam and Dean were behind him. Castiel walked up to Sherlock and sat down across from him.

"Sherlock?" He called.

Sherlock opened his eyes to see the angel across from him. He's a lot calmer now than he was when he first met him earlier, even if he still can't quite wrap his mind around it. "Hello."

"How long is this...train supposed to last?"

"3 hours and 10 minutes, that is if my deductions are correct. Which I'm sure they are."

Castiel sat there squinting his eyes in bewilderment. "How are you doing that?"

"To put it simply, I am a quick thinker and observer. It's elementary, really."

"You learned this technique of yours in elementary?"

Sherlock chuckled. "That's not quite what I was implying but yes, I did develop my deductions at an early age."

"You have an incredible gift, Sherlock."

All Sherlock could do was grin at the fact he got a compliment from an angel. "Thank you."

Castiel smiled and nodded.

"Would you mind if I ask you a few questions? Just to get to know each other? Learn about...angels?"

Castiel nodded. "I understand. A man as inquisitive as yourself wants to learn as much as you can about anything that requires learning and this would certainly be something to learn about."

Sherlock nodded. "Yes. Exactly."

"In that case, ask away."

"How long have you been an angel?"

Castiel sighed. "I think the better question would be how long haven't I been an angel. To that question, I wouldn't quite know how to answer but to your question...since the beginning of time. He created us to serve Him long before he envisioned the idea of humanity. So it was just me and my brothers and my sisters. So many brothers. Just to name a few... Gabriel. Anna. Balthazar. Hester. Uriel." Castiel chuckled for a bit, reminiscing on old, simpler times before the bloodshed and the war. "Uriel, believe me, was the funniest angel in the Garrison. Ask anyone. Were used to frolic in the valley as if we hadn't had a care in the world. We would-" That smile on Castiel's face turned into a gloomy frown when he remembered all of the problems that would come to be.

There was a bit of silence before Sherlock broke it. "Do all angels look like you?"

"Well, this isn't how any of us look. It's hard to explain; the true form of an angel. If a human was to see an angel in our true state, their eyes would burst instantly. This is a mere vessel."

Sherlock scratched his head in bewilderment. "How does an angel acquire a vessel?"

"An angel must contact their true vessel. First, that vessel must prove their faith to the angel, then once they trust the angel, they must decide whether or not they want their bodies taken over."

"Does the same go for a demon?" Sherlock asked, with Moriarty's possession of John in mind.

Castiel shook his head. "Demons don't need a specific host and it's rare a demon even escapes Hell with a specific vessel in mind."

Sherlock nodded. "How is it up there, in Heaven?"

Castiel sighed again. "Nothing like it used to be. To put it mildly, it's practically Armageddon. As Dean told me, Heaven has turned into the most dysfunctional family in the history of dysfunctional families. He's right." He said in a somber tone.

"Castiel, now that you bring up Dean, tell me, why you pulled Dean from Hell?"

"My father commanded it of me. So I obeyed."

It didn't take Sherlock long for him to figure out who his "father" was. "What did your...father...want with Dean?"

"He wanted him to become a vessel for the angel Michael to combat against Lucifer. They were apart of Heaven's prophecy foretelling the battle against Hell."

Sherlock's eyes grew in disbelief, intrigue, and amazement. Then he remembered when Sam said he was possessed by the demon. "The Winchesters? They were supposed to be Michael and Lucifer?"

Castiel nodded.

"Did you pull Sam out of Hell?"

Castiel sighed and didn't want to answer. He slightly nodded. "Please don't tell them."

"They don't know?"

Castiel shook his head. "Not yet. When I did what I did, the repercussions weren't flattering so I would rather wait until the time is right to bring it up."

"I understand. I just have one more question...How is...He? God?"

Castiel sighed. "He was like your average father, I suppose. Now...he's...I've been told he's dead...but I want to be optimistic and believe...have faith that he's out there. Excuse me, I'm craving some peanuts right now."

Castiel stood up and started to walk away. "Wait, one more question." Sherlock called.

Castiel turned around. "I thought that that last question was your last question?"

"There's just one thing I don't understand...earlier, in the car...how did you know where to find us?"

"Simple. I heard Dean's prayer. When he prays for my help, I don't hesitate to answer and arrive wherever he is."

Castiel walked away. Sherlock sat there in admiration. Castiel's loyalty to Dean reminded him of John's loyalty to himself.

Speaking of John...back in London...

We see John/Moriarty walk up to a house. He rings the doorbell. The door opens shortly after...

It was Molly Hooper who answered.

"John? Where have you been? Where's Sherlock? Greg told me you two were in some kind of pickle but wouldn't tell me anymore. He said he didn't want me to worry but I'm really worrying and..."

"Ssh...don't worry. Calm down. I'll explain everything in a moment. May I come in? Been a long day."

Molly nodded, widening the door open and letting "John" inside.

By the way, yes this is supposed to take place during the middle season 6 of Supernatural, after Sam has got his soul back. Strange, I know, but it'll make sense why I used this kind of continuity before the story is over. Trust me.