Cas was sat in the back seat of the impala with Dean driving and Sam looking at a map in the front seat with his brother, they have been driving in silence for over an hour except when Sam was giving Dean directions.
Cas noticed that Dean was pulling up to and old house there was bits of wood falling of the building, it was getting dark out when the boy's left the car to go over the plan again, Cas would stay with Dean and go to the front of the House while Sam came around the back. They were hopping they could corner the Succubus before she claimed her next victim but when Dean and Cas entered the house they could not find no trace of the creature they looked all around the house each room was searched.
"Sam did say this was the house so where is the monster?" Dean looked at Cas with a confused look. "Wait where's Sam?"
" SAM" they both shouted but there was no answer and Dean was getting worried.
"Wait here" with that Dean left Cas alone in the building.
Dean had not been gone long when Cas heard a shout from outside, Cas ran out of the house and looked around at first he couldn't see anyone but the out of the corner of his eye he noticed Dean laying on the floor running to his side Cas noticed blood coming from Deans Stomach. Cas knelt down next to Dean and placed his head onto his knee's.
"Dean" he whispered
"Cas?" Dean opened his eyes and looked up at Cas
"Dean you will be okay, Ill get help, Ill Find Sam." Cas gets up and leave.
" Cas its to late,there.." Dean starts coughing.
" Shush Dean you need to rest " Cas takes of His hoodie and places it over Dean's wound to try and stop the bleeding.
" Listen Cas there something I need to tell you."
"What is it Dean?"
" I...Love you Cas ever since I first time I saw you."
" I love you too Dean" Cas feels tears falling down his face, he knew Dean only said this because he was dying and it hurt him to know he would never had said it any other time.
"Don't cry" Dean whispers, Cas leans over Dean and kiss's him on the lips he felt him kiss back pulling back he looked at Dean and saw he was smiling up at him.
"Just one more thing Cas, keep an eye on Sammy for me." Cas nodded.
He held onto Dean's lifeless body when he heard someone approaching him, he looked up to see Sam standing in the clearing. He stands up " Sam, I'm so sorry."
Sam walks closer to him not saying anything.
"Sam?"
He notices Sam holding a knife covered in blood.
"Sam, what did you do?" Cas was backwards moving away from Sam.
"It's okay Cas, you will join him soon enough."
Cas imminently knows something is wrong this is not Sam it's "Lucifer." he whispers looking at what he thought was Sam.
"Sure is brother." A smirk appears on Sam/Lucifer's face
"It Cant be, we trapped you."
" No well enough it seems." he moves closer to Cas holding the knife higher.
As Cas steps further back when he feels a sharp object stick into his back, he looks down to see blood coming from a wound on his stomach, he realized then he had been stabbed. He falls onto the floor near Deans Body, he feels the intense pain through all of his body looking up he sees Adams face looking down at him, that's when he knew both his brothers escaped from hell.
"Sorry Little brother but we can't have you stopping the apocalypse again."
His brothers vanish from site leaving Cas alone dying. He grabs hold of Deans lifeless hand and looks into those greens eyes he has loved so much. That is the last thing he sees before he dies.