Disclaimer: Not mine.
When Sirius fell through the veil, he immediately spun around and raced back through it. Or rather, tried to. It was then that Sirius discovered that, though it looked like simple black cloth, it felt like a very solid brick wall. Not that he'd ever slammed into a brick wall before. That had been a tree.
He supposes he must have blacked out after that, because the next thing he knew someone was saying "Have a good nap, Sirius?"
He thought it was Harry at first, which was a good thing, because that meant they'd won, or at least not lost too badly. Except the glasses were different (prescription, and he broke them all the time, or lost them, or transfigured them and couldn't for the life of him figure out how to get them back into their original state, until his parents broke down and started sending his a new pair every month without having to be asked), and, no, those eyes just weren't right.
Sirius' thought process came to a screeching halt. "J... James?"
"Oh." Sirius said. "Then... I'm dead?"
"Ah," he said. "Well, that makes sense." And then he scrutinized James, and felt mildly annoyed he was still so young. And that was a rather weird reaction to have upon seeing a long-dead friend, he thought, but it wasn't as if he had much experience in the subject. Unless you count Peter. Which he most certainly didn't.
Once the shock wore off - and it was a rather shocking experience, dying - Sirius thought to ask James where Lily was.
"She comes and goes," he said. "Everyone does."
Sirius frowns; squints. That sounds just a touch too metaphorical for either of them. And then he groans - Oh, fuck - and apologizes, and can't believe he forgot he had something to apologize for. "I'm so sorry, James-"
He waves it away like a skinned knee, instead of the incredible, unbelievable fuckup that it was. "Don't worry about it."
"Don't worry about it? Don't WORRY about it?"
"It doesn't really matter anymore," James said.
"Of course it matters!"
"No," James said, "it doesn't."
Death was a heavy subject for the living. Theoreticians theorized. Philosophers philosophized. James tried to explain it with a Quidditch metaphor.
"James," Sirius said, holding a hand to his head. "Stop."
"Am I not making sense?"
"No, you're making perfect sense. I just have no idea what you're talking about."
"Don't worry," James assured him. "You get used to it, the whole being dead thing."
It turned out being dead was a lot like being alive, except there was less to do and much more time to do it in. This suited James well, because James was a procrastinator and would have gladly squandered eternity.
One thing the dead could do that the living couldn't was step outside the situation. It made things less important, or rather, it had always been unimportant and you were only just learning it. It was in this way that the dead could see that it didn't matter if they were dead.
"Is that supposed to be comforting?" Sirius asked, and James shrugged.
Another thing the dead could do was watch the living.
"That's sort of perverse, mate," Sirius said.
James couldn't stop laughing. "Did you know Remus sings Terrorvision songs in the shower?"
But there were things the dead couldn't do, too, like walking back through the veil. It didn't matter if you strolled up and asked politely, or tried to dart in while it wasn't looking, or just ran full-speed head-on.
"What are you doing?" James finally asked as Sirius picked himself off the floor once again.
"Trying to go back."
"Man, the past is a nasty place to be."
It didn't seem fair to Sirius, that he could have been so very alive, and now he was so very dead. It wasn't fair because everything else was allowed to be something else. Good could always change to bad. Bad could always change to good. Living could always change to dead. But dead couldn't change to living, and it wasn't fair.
"Okay," James said. "Think of it this way: if it's being unfair to you, then that means it's being unfair in someone else's favor."
After a few weeks - Months? Years? Seconds? - of being dead, Sirius sought James out and told him something that he would have thought was very important, if he were still alive.
"Being dead," he told him, "is a nuisance."
"Yeah," James agreed. "But there are good things about it, too."
"Like what? The horrible monotony? The knowing your life was insignificant?"
James grinned. "The listening to Remus' voice crack when he sings Pretend Best Friend."
Sirius disagrees. But James keeps grinning and tries to use another butchered Quidditch metaphor, and Sirius decides these could be counted as good things.