Disclaimer: I don't own Harry Potter.
The Marauders, much like the golden trio, first met on the Hogwarts Express. Remus had been the first to arrive and, not recognizing anybody, claimed an empty compartment. He folded himself into the corner, curling up in his ratty jacket to take a nap.
He wasn't alone long. The first to join him was Lupin's opposite in many ways. Where Remus was average height, sturdily built, James was tall and slim. Lupin's well kept light brown hair was contrasted by the boy's unkempt black hair, sticking up in the back. Even their clothes; Remus's, though lovingly cared for, were patched and tattered, while James's were finely made.
The boys introduced themselves, and then lapsed into silence until they were joined by a rat-like boy, who barely spoke after asking to join them.
The train started moving, and it looked like there wouldn't be any more additions, but just as Remus was curling once more into his jacket, the door slid open, and a fourth boy entered. He was well dressed, but his hair was long-ish and shaggy, and almost looked deliberately messy. He sat down, muttering angry to himself and barely acknowledging the other three with a nod.
The first few hours passed in silence, but slowly a conversation grew, and by the time they reached their destination they were tentative friends. When they got sorted into the same house, it became less tentative.
From that point on, the four shared that same compartment on every trip they took on the Hogwarts express- and it was always the loudest compartment, filled with laughter and joyful shouts.
Years later, when Lupin was asked to teach at Hogwarts, he decided to ride the Hogwarts Express again- just for old time's sake.
He shuffled into the same old compartment, reaching it almost on autopilot. He sat, waiting; for what, he wasn't sure. But as time passed, and students filed by in groups, talking, laughing, catching up from the summer, he remained alone.
When he was shaken in his seat by the train beginning to move, he felt a weird feeling in his chest. The silence was eerie; deafening. It was so much louder than the noise had ever been.
Sighing deeply, Lupin decided to try once more what he'd attempted all those years ago. He curled into the corner, wrapping his old, tattered, patched robe around himself, and closed his eyes. Almost as soon as he did, the door slid open. He heard a mumbled protest, and then a girl's voice said, "Come on, Ronald. Everywhere else is full."
He tuned out their quiet words as they settled in, until a male voice said, "Do you think he's really asleep?"
Some instinct told Lupin not to deny it, and before he really had a chance to wonder why, someone else said, "Looks it, why?"
Lupin cracked his eyes open just far enough to see them, and almost gave himself away at what he saw. A tall, slim boy with James's unruly black hair, and Lily's emerald green eyes. The scar was covered, but there was no doubt whatsoever that it was the son of one of his best friends who closed the door and said, "Good, because I've got something to tell you."
And then his heart broke at what the boy said. Again. He told them about Sirius Black; having escaped from prison to kill him.
It couldn't be true, could it? Twelve year later, and he still had trouble believing it. Sirius, killing Peter, who absolutely idolized the other three Marauders. Sirius betraying James to the dark lord; James, who had treated Sirius as a brother all along; James, who had convinced his parents to allow Sirius to live with him when the Black family had decided he wasn't dark enough to bear their name.
And there was that as well- how would the black sheep of the Black family, who was disowned for NOT being dark, betray one of his closest friends to THE DARK LORD?
Pushing those thoughts out of his head, he relaxed and let himself drift into sleep.
And when the dementor woke him, despite all of his hurt and confusion, it was still memories of the marauders he used to drive the creature away.
Just a random plot bunny. When I first read Prisoner of Azkaban I thought it was a bit careless of Harry to talk about this in front of a complete stranger after being told to keep quiet about it. But hey, Harry didn't always think things through very well, now, did he? I just couldn't help but wonder, though: if Lupin were actually awake, what would he be thinking as he listened to that conversation?