Getting in the car, Dean slammed the door as hard as he could before starting the engine and blasting rock music as loud as his speakers could go. He tried to blast out all the thoughts he was having. "Sam is wrong, I'm not upset Cas isn't here" Dean thought as he pressed down harder on the accelerate step.
He checked the meter, 135km, Dean thought "maybe I should slow down" since he was reaching going downhill soon.
However just when he looked up he saw a deer right on the road and without hesitation Dean swerved his car to the side at full strength and ended up on a different unfamiliar road to the woods. "Dammit!" Dean screamed banging his fist onto the steering wheel. He decided to focus on the road since it was dark and he just had a near death experience.
He was driving carefully when he spotted a limp figure at the side. He knew that figure, that familiar trenchcoat. Immediately he stepped on the brakes to as far as it would go.
"Cas?!" Dean thought out loud.
He got out of the car and in the dim light, he slowly made his way towards the lifeless figure.
When he was closer, he could make out the details of the persons face, "Cas! You dumb son of a bitch!" Dean yelled out in fear and anguish before running towards Cas as fast as he could.
He bent down to pull Cas up into a sitting position.
He felt Cas's skin. It was cold, too cold. Dean started to panic, no no no no no Cas can't be dead.
Dean looked for a sign of life, anything, and then he felt it, a heartbeat, a very weak one, but it was a sign that Cas was alive.

He gave Cas a quick and tight hug before carefully placing one hand behind Cas's back and one behind his knees before lifting Cas off the ground. He jogged back carefully to the impala, heart beating faster and faster as he was worrying that Cas might die anytime. He placed Cas gently in the back seat and buckled him up before running his fingers through Cas's hair and whispering "you'll be alright, I promise" into Cas's ear.
He then got into his seat and started to drive.
Back to the bat cave, he thought , Sam would know what to do.