Harry is rescued from Azkaban by.. Himself? A story of Technology, Magic and Terraforming. Not a crossover.
He told them that when the truth came out, he would never forgive them. They just laughed.
Dumbledore wasn't interested in helping. He'd visited Harry and compared Harry's life and the lives of all his family to pieces on a chessboard. Apparently, Voldemort had given Harry impregnable Occlumency shields. Dumbledore didn't take not being able to freely read the thoughts of his "pawn" well.
Only five people (who weren't involved with Voldemort) believed that Harry didn't commit the crime. The first two were no help, as Cornelius Fudge and Deloris Umbridge wanted to get him out of the way, and to cause him pain. The other three couldn't do anything to help him. Remus Lupin, Neville Longbottom and Luna Lovegood were banned from the court.
Again, you've heard the story many times, of different dimensions. The dementors began to drive Harry insane. It is a myth though, that occlumency helps you fend off the Dementors. In fact, the shields tend to act like an echo chamber, and worsen the effects.
Within two weeks, Harry had suffered as much as someone who had spent two decades with the foul beasts. But he was always able to retain his sanity, by remembering what his Godfather had said. The fact that he was innocent meant that he was able to keep a slim hold on his mind.
That night, unknown to the guards and the Dementors, there was a soft blue glow, and a soft hum that came from the cell. Those who watch the recounting of another dimension's future, where a body is broken down into trillions of parts, moved and then put back together, might have recognized it. However, this wasn't the work of a dimension hopper from the future, 'beaming' young Harry from his hell.
It was actually the work of an older Harry from the past who was rescuing young Harry from the present, and sending him off to train and build a... Well, you'll find out what later.
This had always happened. It's what the people in that other dimension called a 'pre-destination paradox.' Because it had happened, it would happen, and would always continue to happen, unable to be stopped by anyone or anything. Time travel is kind of tricky stuff.
Replacing Harry in his cell wasn't the old Harry... That would happen a little later. Instead, a life-like projection technology took over in the cell, putting out the emotions the Dementors expected, while huddling in the corner in case anyone with eyes looked in.
The older Harry still had some more to do before meeting with anyone, and Voldemort still wasn't strong enough to attack Azkaban and force a confrontation.
Out the high window of Harry's cell, the full moon was in view. And if you looked VERY close at the moon, you might have seen buildings on the surface. But people tend not to notice what they don't expect to notice.
AN: This isn't a crossover. Thought I would say that before anyone asked. I just like the line in the Pilot episode of Firefly with Wash.
Oh, and I don't own Harry Potter.