Dean talks for a little while. Tells Sam about Billie, about shelves full of his potential deaths, about her recognizing, from her new position, their importance. But he soon falls silent and Sam drifts off to sleep. In Sam's dreams, the shelves are more like the shelves in Hogwarts - ornate, wooden, constantly shifting, a moving target laden with heavy leather-bound tomes. In his dreams, he asks if his own deaths are written on those pages as well, and Billie smiles coldly and says what makes you think you get to die?
Then Dean's phone rings.
He knows it's bad as soon as Dean looks at him - that moment of disbelief, the denial aimed at whoever is on the other end. "What? What? But. No. How? Godfucking - how?" The car slows down as Dean seems to lose track of the fact that he's driving, seems to forget how to press the gas pedal.. Sam quickly flips through his mental Rolodex of who is left, of whose loss could bring forth that level of denial, of fear and absolute shock. Jody. Claire. Donna or Alex or Garth or even (God, no please) Jack.
"Where are you?" Dean demands. "Okay. We're a couple of hours away. Just. Just don't move. Don't go anywhere, don't do anything. Stay there. We're on our way." He ends the call and continues his drift, finally pulling over to the side of the road. Sam stares at him and waits for one more piece of his world to chip off and drift away, and Dean finally swallows and says "It's... It's Cas. He says he's Cas."
It takes a second to sink in, and then Sam's world doesn't chip into pieces after all, but swerves violently to the side. "Cas is alive?"
"He says he's Cas," Dean corrects him. "We're gonna find out." He refuses to talk after that, ignoring Sam's attempts with a clenched jaw and a furious glare at the two hours of highway between them and (maybe) Cas.
~~~
An hour into the drive, Dean pulls over again and goes around to the trunk. When Sam joins him, he's loading his gun with silver bullets and digging the angel blade out of its hiding place. "If it's not Cas, I'm gonna kill it."
"Dean, hold on," Sam says, feeling slightly light-headed with panic. "Give him a chance. Don't just -"
"If it's not Cas," Dean repeats slowly, "I am going to kill it."
~~~
When they pull up in front of the phone booth, Dean stands next to the car, staring in disbelief. But Sam already believes. He takes a few steps and the angel meets him halfway and he wraps his arms around his friend and says "oh, God, Cas," and he knows it's really Castiel and that anything is possible.