[I should probably clarify that Castiel and Dean aren't a couple yet and this is my first Destiel story. Hopefully it all turns out decent and that you all enjoy it. Thanks for reading! :) ]
Third Person's P.O.V.
Sam and Dean are on another hunt. They didn't know exactly what they were hunting, that's why there. At a house that was abandoned because of all the supernatural stuff going on.
Dean picks the lock and they both enter the house. They look around with their flashlights. Dean had an Angel Blade, Sam had the Demon Knife and they both had a shotgun loaded with rocksalt.
"I'm gonna go upstairs to see if I can find anything. You stay down here." Dean tells Sam. Sam nods and they part ways, old wood creaking as they walk.
Dean opens a room, the hinges creaking. He looks up and down at the door with the flashlight and them walks into the room. It looks like an old bedroom. To the left, a dirty, old bedframe and a rotting dresser at the foot of it, on the wall. He shines his flashlight to the right and something springs up to him.
Sam is checking a closet using an EMF meter, which is going off. It's a ghost, Sam thinks. He shines his light on the walls of the closet when he hears a scream.
"Dean!" Sam yells, running upstairs. He follows the sound of his scream, he sees Dean kneeling on the floor. A ghost holding his face.
Sam shoots the ghost with rocksalt and Dean falls to the floor.
Sam runs to be by his older brother's side. He helps Dean stand up and asks if he's okay.
"S-Sammy?.." Dean asks, fear creeping up on him. He holds on to his little brother for support.
"Yeah, what's wrong?" Sam asks.
"I can't see...did our flashlights turn off or something?" Dean asks.
"What? No, both of our flashlights are on. Yours is right in front of your feet.." Sam says worryingly. Dean looks down and moves his foot forward a bit. He hears and feels the flashlight move, but doesn't see anything.
"Sammy...I-I can't see anything." Dean says, his voice shaking.
"I'm gonna take you to a hospital. C'mon." Sam says, slight panic in his voice.
With Sam's help, Dean makes it downstairs and into his car. Sam gets in and drives as fast as he can to the nearest hospital.
~Time Skip~
"Sammy...what'd they say?" Dean asks, his eyes wondering. Sam sighs and looks down.
"She said that, there's a slim chance that you'll get your eyesight back." Sam says with a quiet voice, Dean swallows the lump on his throat and nods.
They both hear the flutters of wings. Dean turns his head towards the noise.
"Hello, Sam, Dean." Castiel says, walking closer to Dean.
"Hey, Cas." Dean says, forcing a small smile at the angel.
"Can you fix him, Cas?" Sam asks, instead of greeting him.
He rests his hand on Dean's shoulder for a few seconds, "I can't. So sorry, Dean."
"It's alright, Cas." Dean says, sitting up. "So what the hell was that thing?"
"I shot it with rock-salt and it disappeared and the EMF was going off. So a ghost." Sam concludes.
"Okay. You know who it is?" Dean asks.
"No, not yet."
"Okay." Dean says, he starts to feel uncomfortable. He takes a little while to figure out why, "Hey Cas.."
"Yes, Dean?" Castiel says.
"Can you quit staring at me?" Dean says, moving his wandering eyes to Castiel's general direction.
Castiel looks away, looking anywhere but at Dean.
"How'd you know that?" Sam asks, Dean shrugs.
"I don't know, I just did." Dean says with a shrug, "I felt uncomfortable " He sits up more on the hospital bed, now sitting comfortably.
After a few hours, a nurse came in and told Sam he had to leave. Castiel had only stayed a few minutes with them, so when the nurse leaves, Dean prays to Castiel.
Once Castiel was there, Sam was able to head back home. Castiel took Sam's place and sat in the chair besides the hospital bed.
Castiel watches over Dean every night he's at the hospital.