A/N: I always thought that it was a bit unreasonable for Lupin to make the students show their greatest fear to the rest of the class; after all, imagine what someone like Malfoy would do with the information. Then I realised that all of the example fears were actually very straightforward and easily portrayed, and nothing more abstract like a fear of heights.
For this fic, I am assuming that Lupin ran private boggart tests later with Harry, Hermione and anyone else who couldn't do it with the rest of the class for whatever reason.
Hermione looks at the other two thirds of the Golden Trio, sitting in their favourite corner of the common room, bathed in warm afternoon sunlight. "Well, now that Harry and I have completed our make-up sessions I guess we should look at the boggart essay."
"All right class, settle down." Professor Lupin walks to the front of the classroom, excited chatter quietening around him. "Last lesson, most of you faced a boggart for the first time, and a very good job you all did too. That was step one. Step two is a little more challenging and will be the subject of this week's homework. Carefully handled, boggarts can be useful things; they show us our greatest fear, which can also become our greatest weakness. What you saw was simply the physical representation of you fear, not necessarily the fear itself. To overcome it, you need to be able to interpret and understand your fear. Think about what aspect of you boggart you focused on, and what you felt when you faced it. Think about when you first became afraid of its shape. Think not just of what it shows, but why.
"I understand that these responses are likely to be highly personal and I assure you that they will be held in the strictest confidence. All your scrolls will have privacy charms placed on them as you hand them in, and I will not share the information contained within with anyone. If anyone has any concerns, see me after class.
"Now, to start today's lesson, who can give me some examples of where you might find a boggart…"
Ron shrugs. "I've been thinking about it since class, but I dunno what he wants us to say. I mean, look at mine. They're giant spiders; what more do you need?"
"But, why do you fear them?"
Ron just looks at his friend incredulously. "Freaking hell, Harry. You saw those things in the Forest, they're bloody terrifying! They tried to eat us!"
"Ron, language!"
Ignoring Hermione's interjection, Harry presses his point. "Yeah, but you were afraid of spiders even before then."
"You would be too if the twins turned your teddy bear into one; while you were holding it. It was huge and hairy, and the legs, and the eyes, and then it moved…" He trails off, shuddering at the memory.
Hermione shares a horrified glance with Harry before turning businesslike again. "So you could say that it was the loss of your teddy bear, and its abrupt transformation into something unpleasant that caused the fear. So, the betrayal of something or someone you emotionally rely on."
"I s'pose so." Ron shrugs uncomfortably before changing the topic. "But anyway, what about you? What did your boggart turn into?"
Hermione blushes, the tables abruptly turned. "It was Professor McGonagall. She had my final exam results, and she said…" her voice drops to a horrified whisper, "she said I failed everything!"
She snaps her head up with a glare as a snort of laughter escapes Ron. "That's Hermione for you. You do know that a less than perfect grade isn't going to kill you?"
"No, but it could kill you!" Her reply bursts out of her, silencing him.
"Um, Hermione, actually I'm pretty sure…" Harry trails off as she turns her glare on him, already regretting that he tried to say anything.
Suddenly her glare breaks; words pouring out of her. "No, you don't understand! I'm the one who knows all the spells. I'm the one who knows what we're up against this time and how to defeat it. If I get an answer wrong while we're on one of our 'adventures', someone could die." The trio lapse into awkward silence, Hermione sniffling while Harry and Ron try very hard not to think about just how close they'd came to fulfilling her fear already.
Once again it is Ron who gets the conversation moving. "So, how about you, Harry. What's yours?" His voice drops to a whisper. "Is it … is it You-Know-Who?"
Harry just sighs. "No, it's not Voldemort, it's actually, well, a dementor."
Hermione turns to focus on him, once more composed, her brain shifting into overdrive. "A dementor? So your greatest fear is fear itself?"
"Well. That's deep." Ron looks at him dumbfoundedly before yelping as Hermione's elbow jabs his side.
"Actually I think that's very brave of you, Harry, very Gryffindor. I mean, fearing fear…" Harry interrupts her, shaking his head in denial.
"No, stop. That's what Professor Lupin said too, but it's wrong. A dementor isn't fear; if that's what I was afraid of, surely the boggart would show as itself."
"That's it! That's how you prove what they really look like. I wonder…" Hermione's eyes light up at the idea before Ron's elbow returns the favour.
"So, mate, if your dementor doesn't mean fear, what is it?"
Harry is silent for a moment; his quiet voice when he replies is serious, his expression distant. "The dementor is despair. Overwhelming despair and pain and loss and helplessness, and being so caught up in past memories that you don't have anything left to fight with now. It's hearing my mother screaming and not being able to do anything because it's already too late, and knowing that it's the only way I'll ever hear her voice."
Deep silence follows his speech, the other two afraid even to breathe. Hermione reaches a hand out as if to comfort him but pulls back uncertainly.
Abruptly Harry shakes himself, drawing his mind back to the present. "You know what? I'll write the essay later; I need to go flying." He stands and, without another word, makes his way to the portrait hole. The other two nod, Hermione pulling her half-written Transfiguration essay out of her bag. Harry is right. This is one essay better done later; and alone.