When Harry awoke, three things were clear to him: Sirius had fallen through the veil, he himself had fallen through the veil, and that Sirius wasn't dead.
It was only when there was a giant boom that the fourth thing became clear. Somehow, against all reason and laws of magic he knew, he had somehow ended up on the small island, where he first met Hagrid, and first learned about his true heritage.
Events played out much the same, Harry in too much shock from his recent travel to the past to counter or confirm anything his friend was saying. Fortunately Hagrid took the shock as being something understandable, given the circumstances, and left Harry well-enough alone.
It was when Harry arrived in Diagon Alley that he decided things would be different. Things would go better. This time he'd stop Voldermort from coming back in his fourth year, and stopping the disaster in the Department of Mysteries in his fifth. He'd take steps to ensure the stone was safe, the chamber never opened, and Peter safely in custody.
He planned it all out in his head, every last detail, down to him befriending Ron again to get close to Peter. Everything was going to according to plan.
Until he entered the Great Hall. As he scanned the teacher's table in front of him, something was very much amiss.
"Where's Snape?" Harry hissed to Ron as they lined up to be sorted.
"Who?" inquired Ron, unable to work out who or what Harry was referring to.
"And whose in his place?" continued Harry, unaware of his friend's confusion. The stoutly fellow seemed to be joyously engaged with talking to Quirrell, whose presence failed to make Harry's scar hurt. However, the fact that Lord Voldermort wasn't currently attached to the back of his professor's head was not the fact that troubled him the most.
The man, who Harry later found out was the potions master Professor Slughorn, took an immediate liking to Harry and went out of his way to woo the boy with his many favours. Harry, for the most part, ignored them to concentrate on more important matters.
Harry had decided that such mysteries could wait till later and, at his earliest convenience, stole Scabbers from Ron. Quickly he made his way up to the Headmaster's office, determined to prove once and for all that Sirius was innocent of the crime he was wrongly committed.
Headmaster Dumbledore, an ancient man who had seen many strange things in his time, was perplexed by Harry's insistent demands that the rat presented to him was Peter Pettigrew. He became increasingly worried with Harry's insistence to turn Scabbers back into human and, with no other way of calming the boy, fruitlessly applied the spell again and again to show that Scabbers was an ordinary rat.
Harry's mind raced as he tried to piece it together, angrily screaming at the headmaster to release his godfather, to stop Quirrell from getting the Philosopher's Stone. Dumbledore, temporarily rendered speechless at Harry's knowledge of things he thought were closely-guarded secrets, realized the boy was horrible, horrible mistaken. So it was with a heavy heart that Dumbledore told Harry to sit, as he began to tell a sad tale indeed.
Severus Snape, Dumbledore said, was killed in his sixth year by a prank gone horribly wrong. Sirius Black had tricked Snape into stumbling upon Remus Lupin during a full moon, where Lupin attacked and slaughtered the helpless boy. The repercussions were dire. James Potter, forever certain he could have saved Snape if only Sirius hadn't distracted him, cut ties with his former friends. Peter followed suit, quickly retiring into the background. Of Sirius and Lupin, there was only one fate, and the Dementer's Kiss was delivered swiftly. With three deaths within as many years, Flamel refused Dumbledore's heed to have the stone hidden at Hogwarts, leaving it in Gringotts. By now Voldermort had stolen it, and Dumbledore was unsure what to do next.
Dumbledore pleaded with Harry that, since Harry had displayed Divination powers that rivalled Cassandra herself, that he might be able to help stop Voldermort. That his knowledge of the future might give them the edge over an immortal enemy. Harry said nothing, sitting in the seat, his heart shattered. As he sat there, three things had become clear.
Sirius had survived when he fell through the veil. He too had woken up on his eleventh birthday.
And Harry was never going to see his Godfather again.