The day before his 15th birthday, Dean wouldn't talk about it. Everyone knew what happened now. Time seems to stop and the person you miss most will come and try to get you to leave. If you say no, you stay. If you say no, you disappear. Poof. No one knows what happens after.
There's a pamphlet everyone is required to read. You're supposed to say no. You're supposed to stay and starve and worry. But you have to do it.
Even just a month ago, Dean wasn't worried. Like everyone else, he assumed the wall would fall before his time came. Then it was a week away. Three days. Two. One. One day before what might be the biggest decision of his life. Because stepping out might mean death. But staying… Well, that could kill him too. So Dean acted like it wasn't going to happen.
Sam could see it though. The fear in his brother's eyes. It didn't matter if people were around or not, it was still there. Throughout every conversation he had, every joke he made, it was there. A monster lurking in the shadows.
The day before Dean's 15th birthday passed slowly. To everyone else, it was just another day. But to Sam and Dean, it could be their last day to be brothers. So they didn't talk about it.
When night came, Dean slept in Sam's bed. They didn't talk about it.
Sam fell asleep to Dean's voice, softly singing some Zeppelin song from a long time ago. He stopped thinking about it.
When Sam woke up alone, he didn't think about it.