Sam does he keep talking. He mentions what research he got on the city before he was pulled out of it, the curse of Babylon, the conclusion of which he has no recollection of, and the binds in the books themselves--from the library of the city, that made looking into them that much harder. He drags in another breath and quiets down once the book's placed on his lap.

"You're not crazy," Sam assures, and it sounds almost offhanded but it's not.

"It wasn't just the two of us, Dean." His gaze is filled with intent, and there's a sickening feeling in his stomach as the realization sinks in. Heavy, like a stone. "You were there with me. Or... a version of you, I guess."

Which means he's still back in Bete Noire. Without Sam.