AUTHORS THOUGHTS AND SOME STORY EXPOSITION

SO. I'm gonna clarify some points since it has been illustrated by some readers that they disagree with my logic.

First of all - the timeline of events.

Dumbledore offered to be Lily and James Potter's secret keeper for the Fidelius charm they cast - they refused and told him that they wanted to use their friends instead - Sirius Black to be specific, is the person they chose. (I should also mention that it is never specified who cast the Fidelius charm. In the end, it doesn't really matter to the story.)

So did Sirius persuade them otherwise?

If James and Lily were so certain, it must have been Sirius's persuasion that changed their minds – and that's where the timing became important. Because as they were making these plans, everyone – Dumbledore, Sirius, probably the Potters themselves – suspected someone was sharing information with Voldemort.

Who? They didn't know. So, Sirius convinced them to change their secret keeper to Peter Pettigrew, while James and Lily told everyone that Sirius Black was their secret keeper.

Peter Pettigrew betrayed them - and Sirius Black confronted Dumbledore outside of the Dursley's home. That confrontation as I've written it has left a lot unsaid (Because I don't feel it really matters to the story overall at this point - but since it has come up in questions in the comments, I figured I would explain it.)

First of all, Sirius Black realized immediately that Peter Pettigrew had betrayed them. He also knew that Dumbledore suspected him - and he had to let Hagrid take Harry to Dumbledore while he figured out what to do.

Ultimately, he had to go to Dumbledore himself and reveal information to Dumbledore that was not previously known to him. Namely, his unregistered animagus form.

Keep in mind, Dumbledore is fully aware of the friendship between James, Sirius, Remus, and Peter. The incidents of bullying and the near-death/serious injury of Severus Snape would lead Dumbledore to be very aware of their friendship. The fact that Minerva McGonagall helped them make the Marauders map means that, via Minerva, Dumbledore even knew about the map and that the four boys called themselves the Marauders - he probably even knew about their nicknames for each other (Wormtail, Mooney, Padfoot, and Prongs). It would also cause Dumbledore to be curious about how they were able to hang around Remus when he turned into a werewolf. Therefore, suspicious old Dumbledore, being the kind of crafty old guy he is, would definitely have the suspicion that Peter, James, and Sirius were all animagus - he probably had a few guesses at what their forms were as Animagi as well based on their nicknames.

By appearing in front of Dumbledore in his animagus form, Sirius confirms that information for Dumbledore.

Dumbledore is a talented Occlumens. His use of legilimency is well known - Severus Snape is a legilimens also - therefore the scene I wrote where Dumbledore, McGonagall, and Sirius Black are speaking with Mr. Dursley was also laced with subtext - that being the revelation to Dumbledore that Sirius Black could use legilimency to read minds without having to cast any spells - Just like Dumbledore.

His communication with Dumbledore on the surface was that Dumbledore should read Mr. Dursley's mind - whereas what he really wanted Dumbledore to do was to read his own mind and see for himself exactly what happened - all while keeping things on the down-low with McGonagall.

Sirius Black needs Dumbledore to be on his side - so he takes that opportunity to reveal everything to Dumbledore and get Harry away from the Dursley's grasp. Why away from the Dursleys? Because they're awful and anybody with half a brain would know that.

The tense confrontation between Dumbledore and Sirius in front of the Dursley's happens BECAUSE Dumbledore is suspicious of Sirius Black.

So, some secrets had to be shared, some had to be kept - Dumbledore needed the information Sirius had, and Sirius needed Dumbledore to help keep him out of Azkaban since everybody thought that Sirius Black was the secret keeper of the fidelius charm.

Sirius couldn't go to live with Harry at the Black family's house right away because Sirius's family was primarily made up of Dark Wizards - and Sirius's mother was still alive and living at the house at that time.

So, instead of going immediately to 12 Grimmauld Place, Sirius Black took Harry and went into hiding until Sirius Black's mother died in 1985 and Sirius was able to inherit the house.

Further, Sirius knew he had to go into hiding because he had a responsibility to protect Harry and there were a ton of Dark Wizards out and about who had served Voldemort but had not yet been arrested or convicted.

The reason Remus Lupin was locked away so quickly and was framed by Pettigrew so effectively is that both Dumbledore and Sirius Black had to allow it. Sirius Black demanded a fair trial for Remus Lupin, and Dumbledore tried to get it for him because it was their hope that in a fair trial they would be able to prove that not only was Peter Pettigrew still alive but that he had framed Remus Lupin and Peter Pettigrew was the true secret keeper.

So, in all, Dumbledore and Black had to let what happened to Remus happen because it allowed Peter Pettigrew to believe he had gotten away with it. (This sucks for Dumbledore because Remus Lupin had been Dumbledore's man on the inside in the Werewolf community - Of course Dumbledore is going to try to get him a fair trial. But Dumbledore is not omnipotent - every decision made by the Wizengamot has to be put to a vote - including the decision on whether or not to give Remus Lupin a fair trial.)

Peter Pettigrew knew that Sirius Black was the real secret keeper, however, and he knew that Sirius Black would be looking for him - so he had no choice but to remain in his rat animagus form. He couldn't risk being spotted as a human - most especially since he was supposed to be dead.

Something to keep in mind is that even though Dumbledore is the Chief Warlock of the Wizengamot - he does not have absolute control over the legal proceedings that occur. He can influence things to a large degree, but ultimately everything falls to a vote - which is why, after Remus was imprisoned, he was never given a fair trial. The wizengamot, due to the influence of people like Lucius Malfoy who would threaten and bribe the other members, would never give a fair trial to an inferior species like a Werewolf - especially one that they had ALREADY imprisoned without a trial.

It's important to remember that Sirius Black himself was arrested and charged and imprisoned in Azkaban all without ever getting a trial in the original novels. So, given the sensitive nature of Remus Lupin's identity and the circumstances surrounding his arrest - of COURSE, he was not going to get a trial. If it can even happen to Sirius Black, an important member of a prominent pureblood wizarding family, it can absolutely happen to Remus Lupin, the werewolf.

As for why a lot of this hasn't been explained in detail in the story yet - it is just not important to the story right now.

Remember, even in the original stories the issues surrounding Sirius Black weren't examined in detail until the 3RD BOOK.

We're getting there people - we're just not there yet. :D