The First Good Grown-up
Harry Potter did something amazing in the beginning of Goblet of Fire.. He sent out Owls. This is the Boy who Trusts No One, especially grown-ups. In the first two books, as I shall show, he undertakes dangerous tasks rather than confide in an adult. In GoF, on the other hand, he listens to adults and tells them things. This essay will show that the change occurred in Prisoner of Azkaban when he finally met a grown-up who treated him the way an adult should - Remus Lupin.
In the first two books, Harry does not trust any adult. And he has good reason - until Philosopher's Stone/Sorcerer's Stone, look at the grown-ups in his life. First and foremost are his aunt and uncle, who spent ten years verbally abusing him, neglecting him, depriving him of meals as punishment and lying to him about who he was, who his parents were and how they died. Second are his teachers, who don't seem to notice either his abuse or his neglect and who permit his cousin to bully him unmercifully. Third is Mrs. Figg, who has to treat Harry poorly or the Dursleys would never let her mind him or let him visit her. Harry, of course, doesn't know this, so he takes the crumbs of kindness and stale cake with all the appetite of a starving child. It would be amazing if he could trust adults - or anyone else.
And the results of that lack of trust? That, I think, comes up most strongly in Chamber of Secrets.. He's not surprised that Ron and Hermione aren't writing to him. He can't write to Ron because he's forbidden to let Hedwig out of her cage. However, he might have found a way to send a letter to Hermione by normal post or even to telephone her. He doesn't think about it, though. He assumes that because he hasn't received any messages that they don't care and he's not even surprised - which is why Dobby's plan fails. If he'd had a normal upbringing, he might have been more hurt and maybe have decided to not return. As it was, he still hated the Dursleys more than he was disappointed. They can't betray him because he didn't invest any real trust in them. Yes, he should have, but this is Harry who didn't understand what that meant.
Later in the book, he starts hearing voices in his head. He doesn't confide in any adult at all - even when Dumbledore hints very broadly that he knows something's up, and even what is up, Harry, who loves the man, can't bring himself to tell him. If he had, or if he had told him about Tom Riddle's diary, well, CoS would have been a shorter and less interesting book. Dumbledore would have recognized it for what it was and kept it away from Ginny, and then made use of Harry's knowledge of Parseltongue to defeat the Basilisk without having a not-quite-thirteen-year-old go it alone.
Clearly, even after two years in the wizarding world, including three weeks spent at the Burrow with the Weasleys, Harry still had major issues with other people. Again, given his upbringing, this is not a surprise. Also, as much as he likes the Weasleys and wants to be part of their family, he's not. Mr. and Mrs. Weasley are Ron's parents, not his. No one is his.
GoF breaks a fair bit of the formula, as the center book of a series should do. It begins other than at the Dursleys; Harry is clearly no longer under the Dursley's control - they do not punish him in anyway way, shape or form and he's gotten around that diet; they do not go to Diagon Alley but do spend a great deal of time between leaving the Dursleys and going to Hogwarts. The biggest break, though, is one of the subtlest. Harry is talking to people The Dursleys aren't feeding him? He owls his friends and they send food of varying degrees of edibility and caloric content (I doubt the Grangers' candy helped with the hunger much.) And he trusts that they will do this.
And then he has that nightmare/vision and his scar hurts. And he decides to Owl Sirius. Why? Because he wants to consult an adult - he wants adult advice and help and he trusts he will get it. He actively seeks it out. And he chooses the adult very carefully - in a universe full of father-figures, he chooses the closest he can get to his own father, and someone who is uniquely his. Yes, later he regrets writing to Sirius, but that's for reasons other than trust.
And throughout GoF, he continues to accept help. He allows Mr. Weasley to push him into the woods during the Death Eater attack before he realized his wand was gone, instead of running off to "help". During the Triwizard Tournament, he allows Hagrid, FauxMoody, Cedric and Dobby to help him, and he also asks Sirius' advice. The only person he doesn't listen to is Ludo Bagman, but Bagman is portrayed as such a ridiculous person that it's not surprising that Harry doesn't listen. He didn't listen much to Lockhart, either.
And the help he gets is *real* - it's only because of that help that he was able to get past the first two Tasks. It may well have saved his life for the first Task. That FauxMoody was helping him for his own ends is immaterial in this case - the fact that Harry listened to him is what counts. And Hagrid and Dobby were acting out of friendship and loyalty, and Cedric because Cedric was a decent young man who knew what was fair and right. He was a great loss to Dumbledore's side. However, in SS/PS and CoS, Harry never accepted help directly from anyone other than a close friend. That he does so from his rival and from a somewhat mad professor speaks volumes.
So sometime between CoS and GoF, Harry learned how to trust adults. What happened was Prisoner of Azkaban and Remus Lupin, who taught Harry more than just how to destroy Boggarts or even how to make a Patronus.
Lupin was not the only good teacher Harry has had. McGonagall, Sprout and Flitwick manage to get their subjects across without torturing students and if Snape's methods are not mine, he probably does get a good bit of technique into their heads. I also haven't seen anything objectionable about Sinistra. But he was something special. He knows his subject, he knows how to present it and he knows how to treat each student individually. That first class we see, with the Boggart, is telling. He takes Neville and makes him successful - that it also teases Snape was probably a *plus* so far as he was concerned. Plus he allows each student the chance to figure out how to face their fear and turn it around, except for Harry and Hermione.
In many ways, he's idea. He's fair and trustworthy - he doesn't make promises he doesn't keep and he doesn't treat anyone unfairly. He's also kind to his students. And he's not the authority figure McGonagall is. He doesn't, for example, Head a House (as, given his condition, he shouldn't. Heads of House should be available 12/7.) Nor is he Deputy Head. He's just a teacher in a long line of Defense teachers, and he's young under the grey, and shabby and he knows how to talk to the students.
But even more than that - he clearly cares for Harry. Not to the point of favoring him in class, but in other ways. It starts on the train - when Harry reacts badly to the Dementor, Lupin takes care of him. Which is something that doesn't happen to Harry too often. I'm sure that those times he'd been ill at the Dursleys, he'd been left to cough/sneeze himself to sleep in his cupboard with a warning not to get precious Duddikins sick. Meanwhile, Madam Pomfrey's care has been brisk and professional, as it should be. Oh, Molly Weasley would have smothered him with love and chocolate as well, but I don't think she's had an opportunity to do more than feed him, so Harry doesn't know this.
Later on, though, after the Boggart class, Lupin takes the time to explain why he stepped in before Harry had the chance to do more than begin to see his fear - and in the process makes it clear that he considers Harry's welfare important. He also takes Harry's concerns seriously. Harry needs to know how to make a Patronus because the Dementors are a danger, even if it's currently beyond his level. Harry needs to know more about his parents because, well, he does. Harry is important because he's a thirteen year old boy who has no adult in his life besides teachers, friends' parents and people who dislike him.
Lupin even rescues him from Snape in the Map incident - and Snape was in the right, after all. Snape usually is.
The fact is that most of the adults in the novels automatically treat Harry as if he were The Boy Who Lived (hero worship/denigration) or James Redux. The Weasleys don't, but they have had Harry as a son of their house for a couple of years by the time of PoA. Hagrid doesn't anymore, but he did see James at first and anyway, Hagrid's more child than adult for all his age and size. Snape sees James and all of James' negative qualities. Sirius saw James and all of James' positive qualities (positive and negative, in this case, being entirely subjective.) He's either a walking scar or a monument to a man he doesn't remember.
Remus Lupin sees Harry. Or, more to the point, he sees Lily's eyes, and Harry may look like his father, but he acts like his mother. The clue is the eyes themselves - they're supposed to be the windows of the soul - the pointer to the way he really is.
What do we know of Lily Potter? We only have a few glimpses, but those glimpses are telling. We know she's good with charms because Ollivander says so. We know she's capable of great love and great sacrifice because we've seen her death. And we know a great deal from the little bit we saw in the Pensieve, but we're so busy concentrating on the boys that we don't notice her. What do we see there? She has a temper - a strong one. She can't stand injustice or bullying and will step in even if not wanted - you might call it a "saving people thing." She's impulsive but not to hurt anyone. And she hates poseurs.
Very much like her son. Who sees the world through her eyes, not James' - he's even a Muggleborn in all but fact, just like her. Look at the Shrieking Shack scene, when Harry, a bare month from 14, has to choose if a man lives or dies. I think James in that case would have allowed Sirius and Lupin to kill Peter - and no one would have blamed him. But Lily would not see that as justice. Harry wanted Peter to live so that Sirius could be cleared. I can believe his mother would think that way - not to waste his death. Of course, this last is pure speculation.
But this means that Lupin has a closer idea of who Harry is than anyone else. And Harry can sense that.
He also treats Harry as if he were important just because he exists - not as his parents' son or the savior of the Wizarding World or even a Quidditch champion. He's maybe the only adult at Hogwarts who does. And he makes time for Harry - listening to him, giving him private lessons. This, too, is a new experience for Harry outside his time with the Weasleys. And he can communicate with him, which is something he can't do with the Weasleys. This is finally an adult with whom he can relate, who understands who he is. And if one adult can be that way, maybe there are others.
So, when Sirius shows up and is proven innocent, Harry can trust him. After all, Lupin trusts him - what more does he need? So we get the rather heartbreaking scene where Harry asks Sirius if he can live with him, even though hours earlier, he believed Sirius helped kill his parents and murdered more. But even that's better than the Dursleys. So, Lupin's trust and the fact that Sirius is uniquely Harry's cause Harry to extend that trust to Sirius. Later, it gets extended to others at Hogwarts so that in GoF, he asks for and accepts more help than he ever had done before.
Lupin worked his magic not by spells or wandwaving, or judicious application of any potion besides Wolfsbane, but by his own personality and love for Harry's parents - and then for Harry himself. He also used his skill as a teacher and reached not only Harry but also Neville - both prophecy boys. He showed Harry what an adult could be in the most positive way and so worked a great change in Harry's life. This may have been damaged by FauxMoody and Voldemort on one hand, and Umbridge and Fudge on the other, but for awhile, Harry was almost a normal boy. And we do have Remus Lupin, never a normal boy, to thank for that.