Remus looked between his two friends for a moment and shook his head. "Yes, James, we're pretty sure the castle brought us back. Regulus' house elf spoke to the Hogwarts elves and that's what they said. It makes sense, considering the amount of magic in this castle's very stones. Hogwarts needs magic around to survive, I think. It always seemed a bit sleepy when I'd have to meet Dumbledore here during the summer, as opposed to the energy that could be felt during term."
Getting up off the bed, he tossed Pomfrey's log onto his own bed and paced away from the other two a bit. "But, this isn't pointless chatting. This is important." He turned to face them again, forgetting, in the familiarity, to maintain his usual slouched posture. "You two can't go messing with time just to fix the things that went wrong in your lives. Don't you understand? You wouldn't just be changing your history, but everything that happened because of it, everyone you spoke to, everything you did. You can't predict what havoc you could cause, what other things you could change irrevocably. And YOU!"
He turned to face Sirius. "You'll leave us here to be safe and go off to where you might have to kill yourself? Coc y gath! What is wrong with you? What sort of a plan is that other than selfish and suicidal. Actions have consequences, Sirius. You go back, you tell Dumbledore what happened and then you hope he does something that doesn't throw things even more of than they already are? This is the man who wouldn't even tell anyone who Voldemort really was! We had to die and be brought back by Hogwarts to read about it and hear about it from those who lived it. Your entire plan to save James and Lily without destroying the world rests on trusting Dumbledore with information he likely won't use?"