Hermione gaped at Harry. "Sectumsempra? But that's the hex from the book, the Half Blood Prince's book — and Severus is the Half Blood Prince —" She sat down abruptly, as if her knees had refused to hold her up.

"Somebody else found that book, before Harry?" Ron suggested. "Learnt the spells, and that sort of influenced them?"

Harry's gaze held Hermione's steadily. "I don't think so. Do you, Hermione?"

She shook her head. "No. That's not it, Ron. That's not it at all."

One of them was going to have to say it aloud, Harry knew. He didn't want it to be him, but he didn't want it to be Hermione, either. If I say it, I might still be wrong. He took a deep breath. "Professor Snape's doing it to himself," he said flatly. "He's casting the curse on himself."

"That's why it started at the anniversary of Charity Burbage's murder," Luna said. "Ginny, you were right all along." She paused. "And so was I, of course. July was the biggest clue."

Harry nodded. "The anniversary of her death, the year after her nephew started at Hogwarts. And it got worse so suddenly, when we forced him to go and see her sister." He raked his fingers through his hair. "He even said it. Remember Hermione? When we first suggested he come with us to see Patience Monkshod. He said if she wanted revenge on him for Charity's death, she deserved to have it."

"And it's why the curse gets better, sometimes," Hermione whispered. "It never was my potions. Or someone freshening up the curse at different times. It got worse when he was forced to think about Professor Burbage, about what happened to her. And I suppose everything that went along with it — joining the Death Eaters in the first place. Your mum, Harry. It got better after he'd been spending time — trying to make me a better teacher, and talking about students, and everything."

"Living," Luna said. "When he's living."

"That's what Aberforth meant." Ginny ran her hand over her face. "He never had the knack for making friends … he was hard to like. But she was his friend, Professor Burbage was."

Hermione nodded. "Aberforth did mean for us to know that it was someone taking revenge for Charity Burbage, after all. Just not the person we thought it would be."

"How did Aberforth know?" Ron asked. "I mean, know Snape was alive, in the first place. And know what was wrong with him."

"You hid him in the Room of Requirement, didn't you?" Neville asked Hermione. She nodded. "Then I bet Ariana told him. Or showed him. It's dead bizarre, the way the Room lets her have her way with it." He frowned. "I really believed he wanted us to solve it, you know, that Snape did. I suppose I shouldn't be surprised that he's a good actor."

"I think he did want us to, does want us to," Hermione said. "I don't think he knows he's doing it to himself."

Neville's eyebrows went up. "How can you cast a Killing Curse if you don't know you're doing it?"

"The same way you bounced when you were thrown out of a window as a kid, and I grew my hair back overnight," Harry said. "They teach us at school to always use wands and always use incantations, until we're so used to it that wandless magic, silent spells, are hard or even impossible to learn — but it's the first kind of magic most of us ever use, isn't it, doing things without understanding what we're doing or even that we're doing it?"

"And Snape can do both," Ron said slowly. "Deliberately, I mean."

"But that doesn't make sense," Neville said. "Because if he's doing it silently and without a wand, how did Aberforth know?"

"Well, it happens when you're really upset about something," Harry said. "Like me inflating Vernon's horrible sister. I didn't mean to do it, I didn't know I was doing it, and I couldn't stop myself." He shrugged. "I still get the occasional midnight howling horrors over Cedric Diggory dying, and I didn't really know him and he didn't suffer. What kind of dreams do you think Professor Snape has about what Riddle did to Professor Burbage?"

"So we just tell him he's put the curse on himself, and he can stop doing it, and that's that," Ron said.

"Like George stopped drinking, that year after Fred?" Hermione said. "Because people told him it was bad for him?" She shook her head. "You don't just get over things because someone points out you haven't."

"Yes, but George did stop," Ron pointed out.

"Because Harry and I dragged him to therapy, three times a week, for eight months," Hermione said.

"And thank Circe's sacred socks we found a shrink who was a Squib," Harry said. "Or I'd still be doing the paperwork on all the Obliviates."

"So drag Snape along to the Squib shrink, then," Ron said.

There was a small silence as all six of them tried and failed to imagine Severus Snape in therapy.

"There is something we can do, you know," Luna said in her silvery voice. "I mean, we're already doing it, aren't we? And it seems to be working." She looked from one confused face to another. "Be his friends."

"Be Severus Snape's friend," Ron said flatly.

"He's not that bad," Hermione said.

Ron raised his eyebrows. "He's about exactly that bad, Hermione. He's exactly the same rude, sarcastic, greasy git he was the entire time he was teaching us."

"The same rude, sarcastic, greasy git who saved Harry's life? Who risked his own life to spy on Voldemort for the Order? Who did every single thing Dumbledore asked, no matter what it cost him?"

"I'm just saying, it's a lot easier to admire him for all that from a safe distance," Ron said, and Neville gave a snort of laughter. "When he's not right in front of me, doing his best to make me want to punch him."

"Just because he's hard to like, doesn't mean we can't try," Luna said. "Professor Burbage liked him, didn't she?"

"Shall I ask him out for a pint, then?" Ron asked. "Oh, that's right, he can't go out in public. Suggest a quick game of chess?

"Ask him about Defence Against the Dark Arts," Ginny suggested. "Tell him you want his insight onto where the jinx might be hidden."

"Tell him I've asked you to help with the Quest," Hermione said.

"How is the quest for the Quidditch Key going, anyway?" Neville asked.

Hermione shrugged a little. "They still haven't started looking, so not very well. But at least it's keeping them in the Library, and not wandering the Forbidden Forest."

"Do you want me to drop a hint at some point?" Harry said. "I mean, much longer and they'll get bored of the idea." He grinned. "They are only eleven."

"We didn't get bored looking for the Philosopher's Stone," Hermione pointed out.

"Well, one, we had Tom Riddle as an incentive," Harry said. "And two, Ron and I would have stopped ages before we uncovered it if you hadn't kept nagging us."

"Harry and I can make it seem completely natural," Ginny said. She turned to Harry. "Gee, Harry, I wish I'd had the Quidditch Key that time I had to sub in as Seeker for you. A way to make the Snitch fly straight for you would have been super!"

"I know, Ginny," Harry said. "I hope no students find it before we do — it would guarantee their House winning the Cup!"

"That's about as natural as Madam Rosmerta's hair-colour," Ron said.

"We'll make it work," Ginny said cheerfully. "Harry's used to being all deceptive, because, Auror. And I'm just naturally gifted."

"Back to Professor Snape," Neville said. "I get the idea of sort of cheering him up —" He stopped. "I just said that out loud, didn't I? Cheer up Professor Snape?"

"Distract him," Luna said softly. "Give him things to think about that aren't the War, and what he did, and what he wishes he had done."

"The day he spent creating the Quest, the curse shrank by about two-thirds," Hermione said.

"Right, so, that's good," Neville said. "But it's not going to get rid of it, is it? And what happens when we all go home for the summer? Is someone going to take Professor Snape home for the holidays to make sure he doesn't start brooding on things again? Because, and please don't take this the wrong way, Hermione, bags not me if that's the case. He might not be my Boggart any more, but he's not exactly social, is he?"

"He can come with Daddy and me to Sweden," Luna said. "I don't mind. And an extra set of eyes to spot the Snorkack would be quite helpful."

"Oh, Merlin's beard," Ron said quietly. Harry had a sudden vision of Severus Snape dragooned into a hunt for one of Luna's impossible creatures, scrambling up hill and down fjord. He caught Hermione's eye and they both grinned. "Please don't take this the wrong way, Luna, but —"

"But we don't need to worry about that now," Hermione said firmly. "Look. We need a two-stage strategy. Stage one is keeping Professor Snape alive. That means all of us, Ron, have to spend time keeping him, as Luna said, distracted."

"And stage two?"

Hermione bit her lip. "Stage two is obviously making sure he gets over blaming himself for Professor Burbage's death."

"That's not the only thing he's responsible for, though, is it?" Ron pointed out. "I mean, alright, he had to keep his cover, so I won't mention the students who were beaten and tortured when Snape was Headmaster. Or George's ear. But nobody forced him to join the Death Eaters, and nobody forced him to tell old Holeyshorts the prophecy."

"Don't you think he's paid for that?" Hermione said. "For a mistake he made, all those years ago,when he was young?"

"Not that young," Ron said. "And how old do you have to be, anyway, to know that signing up to someone calling themselves a Dark Lord is probably a very bad idea?" He looked at Harry. "Your parents knew, Sirius and Lupin knew, Neville's parents knew, my parents knew, right from the get-go."

Harry remembered how horrified and unhappy he had been after viewing Severus Snape's memory of being humiliated and taunted by Harry's own father, in front of jeering onlookers — how he'd felt himself, in the same situation — remembered Sirius and Remus admitting that his father had carried on targeting Snape for the rest of their schooling. "I imagine that was part of it," he said quietly. "He and my Dad hated each other from the day they met."

"That's like saying Draco became a Death Eater because you and he didn't get on," Ron said impatiently. "Snape's the same age as your parents would be, Harry. The First Wizarding War had been going on for years when he joined. People were being murdered. If we'd been around, we might have been murdered — Hermione for being Muggle-born, and us for being her friends."

"And if Severus Snape hadn't changed sides, if he hadn't started spying for the Order of the Phoenix, the First Wizarding War would have been the Last Wizarding War," Hermione said. "Ron. I'm not blind to the fact that he signed up to an organisation that would have killed my parents and me just for being what we are. But that's one year, in a whole life. Should we just let him die, because of that one year?"

"I'm not saying that," Ron said. "All that was true when we found out about the curse, and set out to try and break it. I'm just saying that a quick chat over a cuppa to remind him that he couldn't have single handedly taken on however-many Death Eaters were there when they murdered Professor Burbage isn't going to cut it, is it? Because either he's still the same man who only switched sides in the hope he'd get to comfort the widow —"

"He isn't," Harry said with certainty. "In the Pensieve …" How many men and women have you watched die? Dumbledore had asked, and Snape had replied, Lately, only those whom I could not save. He shook his head. "He wasn't, long before the end of the War."

"Then he's got a fair bit more on his conscience than one death, doesn't he?" Ron said. "Who gives absolution for that?"

"I might have an idea," Hermione said slowly. "I'll have to think about it, for a bit. But it might work."

.

.

.

Author's notes: The Pensieve memory Harry recalls are quotes from the book. In Deathly Hallows, Ariana's portrait clearly has a different relationship to the passage it conceals than other portraits, although what and how exactly isn't clear — so I ran with it.

As you can see, I'm extrapolating a fair few things about magic and how it possibly works from hints and throw-away lines, as I did in Chapter 46 with the Boggart and when Mike Rowland subconsciously used the Supersensory Spell.

What mad idea does Hermione have — and how badly is it likely to go?