This is a coda to Reading Is Fundemental.

"Sam."

Sam Winchester swung out of bed, all ideas of sleep gone, staring at the hospital gear/trench-coat clad angel looming above him, curious look peering out at him.

"Damn, it Cass." Sam gasped, blinking heavily. "Don't you normally do this kind of thing to Dean?"

"I do. But it's not him I wanted to see." Castiel proceeded to do his customary head tilt.

"What's up?" Sam asked, planning on getting back to sleep as quickly as possible, given his absolute headache of a day. What with angels, a prophet, and a lump of rock that had inside it the word of God, Sam really could do with at least four hours sleep. Which would actually be a luxury for the Winchester brothers.

"I'm having trouble, as an angel, with placing certain... feelings." Castiel said, sitting down on a wooden chair, and Sam blinked. That was one of the sanest things Castiel had said all day, not that Sam would admit it.

"What kind of feelings? Regret? Anger?"

"No, I understand those feelings, especially regret. Thank you, by the way."

"What for?"

"For pretending to forgive me."

"I wasn't..."

"I was more asking, if it's normal for someone to feel... indebted to someone. Like they owe them... a large part of themselves. Perhaps more."

"What do you m-..."

"I mean, like the world is crashing down around them if they aren't in a certain distance of the person in question. Like they can't deal with it, or do without them."

"That's... love, that's love, Cass. Who do you...?" As realisation dawned on Sam, his jaw went slack, eyes wide. "Cass... do you... do you love my big brother?"

Castiel said nothing, just stared out of the window, gazing at the twinkling stars.

"When I said that we share a more profound bond, I meant it. When I say I trust him... I trust him with my life."

Sam just stared at Castiel, and it was far too apparent that Castiel was serious.

"Cass, why are you telling me this?" Sam asked.

"I'm not ready to admit anything to Dean. Despite my obviously more... eccentric demeanor." Sam could agree with that. "Dean could reject me... or worse."

There was a moment's silence, before Sam realised Castiel was waiting for him to break it.

"Cass, Dean's outside in the Impala."

Of course, the angel vanished in a blink.

And of course, Sam never really went to sleep that night.