Cas put his ear against the phone, watching Clara with mild confusion about what was going on. She had looked annoyed that they had been interrupted in their tree decorating ventures, which Castiel was just starting to enjoy just a bit. He almost a bit disappointed that it had been interrupted. He was sort of enjoying getting to know the woman again. However, the moment Castiel ever started to enjoy anything, it was inevitable that they would be interrupted.
"Hello?"
He waited for a reply but when none came, his eyebrows furrowed slightly. He heard Clara talking loudly to the people at the door. He could here a slightly bothered twinge to her voice, but the people at the door didn't. The people to enter the living room were not Clara at first, but soldiers dressed in all black followed by an older blonde woman in a bob who he assumed to be Kate. He heard the door shut and Clara materialized behind them a few seconds after, moving past them next to the angel. Kate was the first to speak, addressing the two people standing in front of her while she waved a hand to the soldiers to indicate for them to disperse through the house.
"Sorry for being so pushy, Clara, but something else happened."
Clara immediately straightened, "What kind of something else?"
"We...-" Kate paused, her gaze switching to the angel after a moment, just registering that there was someone she didn't know in the room.
"Who's your friend?"
The brown-haired woman paused, and as Cas knew she was trying to think of a quick excuse of why he was here. However, Cas had her covered. Just as Clara began to form an explanation, the angel cut her off.
"Special Agent Novak. FBI."
The angel pulled out the most recently made badge that Dean had given him, flipping it open and showing it to Kate. The blonde woman blinked, before she took it from the angel to examine it. The angel had gotten better at faking his identity, especially after his time alone.
"As you mentioned on the news, a majority of the cases are from America. I was sent by my superiors to help your investigation in any way I can."
Kate stared at the apparent FBI agent for a few long moments, before handing him back his badge. Clara moved a bit closer to the angel, in a slightly protective sort of way.
"Bloody Americans. Alright, Clarence, not to be rude, but I would like to talk to your superiors before you get fully involved in the case."
In response, the angel reached into on of his front pockets and handed Kate a card. She paused, before she took the card, glancing at it before taking out her phone again. However she didn't call yet. Kate had one more question.
"I'm not done yet. Why are you here in Clara's apartment? You should be getting cleared at Headquarters. Not by me. Not that I can't clear you, but still."
Clara answered this one before Cas did, looking up at Kate.
"He was dropping off his stuff. Clarence is an old friend of mine as well as an FBI agent. He was going to stay in spare room while in town. Not to mention, he is a quite knowledgeable in this kind of thing. More than the FBI knows, by far."
Kate looked between 'Clarence' and Clara. She gave a small nod in understanding. Kate looked directly at the angel.
"So you've met the Doctor then?"
"We are... acquainted."
A small smile touched the woman's face momentarily, which slightly confused the angel but that didn't matter. She was buying the story, it seemed. Even so, she was typing the number into her phone.
"Then this call to your superiors is just a formality. Any friend of the Doctor's is a friend to UNIT."
She put the phone to ear after she finished dialing the number.

An ocean away, the phone now labeled FBI in the Winchesters' bunker began to ring. Dean was sitting two tables away, nearly falling asleep as flicked through books that the Men of Letters had written on anything about the Mark of Cain. He sat up when it rang, looking around to see if Sam was around to get it. It was then he remembered his younger brother was out picking up food and pie. Dean got to his feet, the chair noisily scrapping against the ground. He crossed the room picking up the phone. I female voice was at the other spoke immediately.
"This is Kate Lethbridge-Stewart with the United Nations Intelligence Taskforce calling to confirm that Special Agent Novak is indeed supposed to be on British soil."
Dean paused, mentally questioning what the hell Cas had gotten himself into. First, why was he in England in the first place and how on Earth had he somehow gotten tangled into something involving the United Nations. He heard the door open and close and saw his younger brother come in holding a fast food bag. Dean responded to Kate while giving a confused look to his brother.
"Yes, I did send Agent Novak to British soil to look into a case. I knew he could be an asset. I can confirm that."
Sam looked up at Dean, mouthing at him "What?" Dean shrugged, pointing at the phone. Before he could try and respond to his brother, he heard the UNIT agent speak again.
"I just needed you to confirm that. I won't be calling again."
After that, the line went dead. Sam immediately spoke up, taking a salad out of the bag.
"What was that about?"
"Dude, the United Nations just called."
"You're joking."
"We need to call Cas in an hour or so. Apparently he's in Britain getting tangled in a United Nations thing. Probably should make sure he has things under control across the ocean."

Back in Clara's apartment, Kate dropped her phone back into her pocket.
"Everything seems to be in order. Right, where was I...?"
Castiel responded, while Clara grabbed the remote to the television and muted it. After muting the television, Clara dropped onto the couch, grabbing her cup of tea and sipping at it.
"You said that something else occurred, related to the disappearances."
Kate nodded, looking between Cas and Clara. She still seemed slightly weary of the stranger listening in, but she focused her answer equally between the two people anyway.
"One of the missing people was spotted in London a few hours ago. A man named Richard Cartier. Went missing a day after the shower, and he was just walking up the streets on London. Devout Christian. Father of 2. Never divorced and his wife is waiting for him. A local officer spotted him and brought him in for questioning. Apparently, he barely remembers anything about what happened to him, though we are quite sure he is hiding something. We were thinking Clara might be able to get him to talk."
Clara looked up from her tea, looking a bit confused. The short woman got back to her feet and walked over to the two again, forming a triangle between Kate and Cas. She looked over at Kate.
"Why do you think I would be able to get him to talk? Don't you have people to do that for you?"
"He isn't a criminal, he is a victim. We can't use any methods to force him talk. However, the only people we have on hand are UNIT agents in our base, and they can be a bit intimidating to most people. You can tell when someone has been a soldier."
Kate's eyes momentarily moved to Cas, before they moved back to Clara. She continued.
"You aren't a soldier. You are a school teacher. You might be able to coax the information out of him."
Clara paused, before she slowly nodded.
"Alright, I see your logic. We'll come."
"I thought you would. Everyone, to the van."
The soldiers and Kate left in a quick fashion, causing Clara and Castiel to be left behind. The two walked down the stairs together. Clara spoke in a low voice.
"What do you think?"
"I think Richard Cartier sounds like the kind of person Arariel would take as a vessel. From the way that woman described the person's behavior, it is likely Arariel is still in there. He is just masquerading as his vessel."
"So it seems like we have a bit of work ahead of us."
The angel nodded as they walked outside into open air.
"Yes we do."