História Winchester's go to London - The demon:

I stood there confused on how this Sherlock guy even knew that me and Sam were brothers. I watched the road with this very thought in my head. I almost thought my eyes were playing tricks on me because as this one woman walked past her eyes turned black.

Erasing my last thought I start to run towards her. From the corner of my eye I seen Sherlock and his partner John stop mid way arcoss the crime scene. From behind me I hear Sam's footsteps chasing me. Apparently Cas never moved because I never seen or hear him.

  Just as I get close to her her head shoots up towards the sky and a thing of black smoke starts to come out. Sam rembering how to get a demon back inside their vessel starts saying the excorism backwards really, really loud. Finally close to her the demon is back in its vessel.

Grabbing the demon by the hand I wait for Sam to come with a blade. Once he does we both see the three detectives walk our way with confused expressions on their faces. Cas out of his daze starts walking our way to.

"What the HELL was that?" John asks as soon as he was close enough.

"That Dr. was a Demon if you must know." I say with irritation in my voice.

"Who are you?" I hear Sherlock say from behind everybody.

"I'm Dean Winchester and this is my brother Sam. We are American Supernatural Hunters."

"So your saying that monsters are real?" Lestrade asks not believing me.

Ignoring him I turn around and grabbed the angel blade from Sam. About to go and kill the thing Cas stops me mid way.

"What Cas?"

"We could get answers from her."

"It's a Demon! It's not going to tell us anything."

"It's always worth a try Dean."

"Fine... Sam can you go get the cuffs from the trunk of the Impala?"

"Yea keys?"

Tossing him the keys he jogs over to get them.

"I won't tell you and your angelic friend anything." The Demon says after awhile.

"Angelic?" John asks confused.

"It's means Angel John." Sherlock says amused.

"Angels? Angels are real?" Lestrade asks shocked.

"Yes vary much so Detective. Your staring at one right now." I say pointing at Cas.