A/N Hey guys. This story is a crossover of Supernatural and the Avengers.; It follows the movie's main plot but will branch out slightly due to the Winchesters and Castiel appearing. The Winchesters are from season 8 just after they have found the bunker however before Sam starts the Trials. WARNING: Mature language

I don't own Supernatural,Avengers or any of their characters

Sam knew keeping secrets had consequences especially when they were from his brother, Dean. It happened when he didn't tell him about Stanford; it happened when he didn't tell him about Ruby and the demon blood; it happened when he didn't tell him about being soulless and it happened when he didn't tell him about Amelia. It wasn't that he didn't trust his brother it's just Dean like every Winchester had developed the stubborn and hot head trait meaning that telling him could end in either two ways. One would be getting punched in the face and, two would be getting a stream of hurtful words and anger.

So when Agent Coulson rang that morning , Sam knew he was fucked.

It was early morning, Sam was in the library looking through the Men of Letters' vast knowledge or 'geeking out' Dean would lightly put it.

"Dude, don't you know the meaning of sleep" Dean said, entering the library in his new robe with a cup of coffee.

"I do and I have been getting sleep" Sam stated, not removing his eyes from the book he was previously reading before Dean came in.

"Because falling asleep with your head in a dusty book that will mostly cause neck ache is sleep" Dean joked, his voice full of sarcasm, "I mean, have you even tried the memory foam in this place."

"Yes, Dean." Sam said blankly, not engaging in the conversation.

Dean sighed and sat down across from Sam, he took a sip of his now lukewarm coffee and took a peek at what Sam was reading.

"What are you researching, anyway ?" Dean asked.

"Djinns" Sam stated still not lifting his eyes from the book.

"But, we know everything about Djinns". Dean said.

"Not everything," Sam remarked, finally looking at Dean rather than the book "So get this…"

"Hold it" Dean interrupted, " It's too early in the morning for this and all I want to know about Djinns is their powers and how to gank them".

"And let me guess since you're reading that book again, there's no news about closing the gates of hell or a new case". Dean continued, drinking the rest of his coffee.

"Yeah" Sam admitted.

They had been waiting for some news about the Gates of Hell since finding out that you could close it but there hadn't been anything yet and then suddenly it seemed like the supernatural world had suddenly taken a day off which was strange.

"I'm sure something will come up though" Sam said when a phone call from his phone interrupted abruptly.

"Hello" Sam answered when answering the phone

"Mr Winchester, it's Agent Coulson from S.H.I.E.L.D. I worked with you as well as Dr Selvig with program P.E.G.A.S.U.S ." Agent Coulson addressed.

Sam stiffened when hearing the voice of Agent Coulson. While Dean was in purgatory, before Amelia happened, Sam helped S.H.I.E.L.D with Program P.E.G.A.S.U.S or the Tesseract, knowing a few things in that field of area with Stanford and of course being a hunter because of it's supernatural properties however that was it,he didn't become an agent and he never started working for them. He never would have figured that they'd call again for anything once he had served his purpose.

"We've realised, you have moved somewhere of the grid in Kansas and had no other way to contact you." Coulson continued.

Sam noticed Dean looking and knew he realised how he stiffened when he first answered the phone, that meant he couldn't just place this off as a normal call.

"Look" Sam started, knowing where this would go.

"We need you back," Coulson declared, " I can't speak about the details on the phone, so meet me in Kansas, Lawrence in the abandoned barn closest to your parents house and we will speak more on the matter."

Sam sighed and pinched his nose, he did not want to get involved with this especially now that his brother's back …. But he knew that he couldn't turn this down either way, he had no choice in the matter, " Alright , I'll be there."

"And Sam" Coulson paused, "Bring your brother."

The other line on the phone clicked signalling that Coulson had hung up.

"Want to tell me what that was all about ?"

"So you're telling me," Dean paused, clenching the Impala's steering wheel in anger, his knuckles turning white, " You were the Government's bitch while I was away."

"I wasn't their bitch. I just did some work for them." Sam explained.

"What even is this program P.E.G.A.S.U.S ?" Dean asked.

"P.E.G.A.S.U.S. stands for Potential Energy Group Alternate Sources United States. It's aim is to analyze the Tesseract." Sam informed, looking outside to see Lawrence.

"The Tess… what ?" Dean asked.

"The Tesseract". Sam corrected.

Sam went silent, not wanting to talk about the subject anymore but the way, Dean was looking at him; he knew, he would have no choice in the matter just like S.H.I.E.L.D. " Tesseract was recovered by Howard Stark. I was recruited to see if there were any Supernatural properties to it." Sam explained to Dean.

" And did it ?" Dean pressed.

"Of course it did" Sam answered, turning to Dean , "With that much energy and power, it definitely wasn't natural. I looked through the lore a bit and found out it was one of Odin's crown jewels."

"Odin as in the Norse god." Dean said.

"Yeah" Sam confirmed. With not much information about it, it was a weak theory but some questions from Mr Rogers or mostly known as Captain America. It started to grow and after 6 months, it was confirmed.

"I only worked there for 6 months. Once the theory was confirmed, I left." Sam continued.

"You weren't with Amelia for all that year." Dean said.

"No" Sam murmured.

" So, you lied… again" Dean remarked, angry, "Nice to know, you're being really truthful lately."

"What do you want me to say, Dean. It was confidentiality" Sam countered.

"Who was I going to tell, the whole of the United states." Dean barked, " It's nice to know, you don't trust me."

" I do trust you" Sam said and sighed , " Can we not fight, please." Pulling out the 'Puppy dog' eyes.

"Stupid, 'puppy dog' eyes" Dean muttered.

They continue driving in silence as they reached their deserted destination. The barn was clearly abandoned with gangly ivy and moss riddling the now rotten wood, giving the brothers an eerie feel.

"This isn't creepy at all." Dean commented, looking at the old barn.

"He definitely meant this place, there isn't another barn like this for miles." Sam observed.

"Well I don't trust the guy." Dean remarked.

Sam rolled his eyes at Dean's lack of trust, " You haven't even met the guy." Sam contended.

"Exactly" Dean emphasised , " You even said yourself that you did the job, you were assigned to do; now they suddenly want you back, it's suspicious."

"Maybe they just need me to look over something," Sam suggested, " Something simple."

"I doubt it." Dean muttered

"I assure you, Mr Winchester." Agent Coulson stated coming out of the shadows produced by the barn, " That it's in the world's benefit that your brother returns to work for us."