"We didn't want to," Remus said softly, looking at the book in his hands rather than his friends. "Looking back, I think there were signs. We knew there was a mole. But, we didn't want to see them. Didin't want to believe it could be one of us." His friends had been willing enough to believe it of the werewolf, though. They'd suspected Remus, included Peter. At that was a bitter thought. But, not one Remus was willing to air at the moment. What did it matter now? "War changed all of us, forced us to do things we never would have thought we could, brought out personality traits we may have tried to ignore or keep hidden. It was inevitable we grow apart a little after school. The war exaggerated it, I think, created a situation in which our differences became more prominent than our shared past. Life happened and four boys who'd gotten too full of themselves in school had a deadly and rude awakening to the real world."
Taking a deep breath, he lifted his head, focus firmly back on the present. Dwelling on a past they couldn't change wasn't going to get them through this crazy present. "But, I don't think going back is going to be an answer, even if it's possible. There are too many variables. Too many things that could go wrong. Would we even be going back to our original timeline? Or would find ourselves in a branch created by our disappearance? Would there be another version of us, even, still living in that timeline? And what would you change? Not make Peter the secret keeper? Turn him in? What would that do to the prophecy? To the war? How many more people would die before he could be stopped? How much longer would Dumbledore have continued to move us like pawns on a chessboard while keeping vital information from us? Could we even change something fated to happen? Or would Fate find another way to kill James and Lily off, leave Harry an orphan? Maybe take us out too, this time, so he remained alone? And all of that only applies if we're even able to remember all of this, if we're not simply thrust back into the exact moment when we left with no recollection of our time here."
It was Remus' turn to sigh as he leaned his head back against the headboard. "There's a reason the Ministry regulated the use of Time magic. It's too dangerous to mess with if you don't know what you're doing. We only managed this because of the castle and, honestly, I'm still not sure this is time magic. It could be death magic, the castle bringing people back from the dead at the ages it liked best or the ages at which our magic was the right sort to shore up it's own. The castle's sentience isn't like that of a living organism. Who knows what it really did to bring us all here?"