Castiel's eyes opened wide and he dropped his knife has dean pulled him into the kiss. The warm hands he had gripped tight and raised from perdition around his shoulders and his scent overwhelming Cas. It couldn't not be him. How could it not be him? How could this be a demon? It had to be Dean. His dean. The kiss ended and he looked into Dean's eyes and said his name longingly. Only they weren't his eyes, they were black and cold and glaring as a sharp knife was plunged into the helpless angel's chest. "Dean is dead." Snapped the cold voice as Cas was filled with sharp horrible pain, and even worse the terrible despair. Dean save me. My dean please save me. He thought as tears brimmed in his eyes. "Help" he managed to gasp out. The demon laughed,"No one's going to help you. Especially not your Dean." Cas tried to imagine dean's face, his dean, but the pain was so strong, blood was staining his trench coat turning it from tan to red. The demon whispered into the dying angel's ear,"He never loved you as much as you did. I have his mind- I know that." And then he laughed as the blue light faded from the eyes of the angel in the red stained trench coat, no longer able to think of his Dean.
Disclaimer: I'm on season one of Supernatural. I haven't even met Cas yet. I just know a lot because of tumblr.