Hermione clutched her nearly empty mug. "What? What completely mad idea?"

Harry shook his head slightly, as if to settle his brain in his skull. "Someone who knows Lucius Malfoy. Honestly, I don't think Lucius has been close to one person who wasn't a blood relation or a Death Eater."

Hermione bit her lip. "I suppose."

"Hermione." Harry put his mug down and leaned forward. "You asked me about Death Eaters people thought were dead, but aren't. You've been talking to someone who knows Lucius Malfoy well enough to be confident he's not the source of malice. And someone inside Hogwarts in trouble — has been cursed, given what you were looking up — and it's someone who's extracted a promise from both you and Minerva McGonagall to keep quiet about him." He paused, and then said very quietly, "Hermione."

"I promised that I wouldn't tell you!" she cried.

"If I use Legilimens, you won't be telling me, would you?" Harry paused. "Would your promise make you feel you had to fight me?"

"I'm not sure," Hermione admitted. "But — I think I might, anyway. I hated the final year D.A.D.A classes where we had to try and learn Occlumency."

Harry gave a wry smile. "I didn't much enjoy learning it, either. But Hermione — not just as your friend, but as the Defence Against the Dark Arts Professor of Hogwarts, and as an Auror — if I suspect someone at this school is suffering a Dark curse, I have to find out. You understand? It's actually, technically, my job and my duty."

Hermione braced herself. "I know."

"I hate to think of hurting you, though," Harry said quietly. "So let's try one more thing. Hermione — is it Draco Malfoy who's in trouble?"

"No," Hermione said. "At least, not that I know. I haven't seen him for a few weeks, though."

Just as quietly, Harry said, "So if it isn't Draco — Hermione, is it Professor Snape?"

"He —" Hermione didn't have to decide whether confirming Harry's speculation would count as telling him, or not, because Harry took one look at her face and erupted to his feet.

"Merlin's bloody buggering bollocks, Hermione!" Pulling out the Marauder's Map, he rapped it with his wand. "I solemnly swear I am up to no good. Do you know how often I've wished he was still alive? The things I've wished I had the chance to tell him, to ask him?"

Hermione bit her lip. "Harry …"

"How long have you known?" he asked, studying the map. "I mean, I know it can't be long, because you're the worst liar I've ever known."

"Just since I got back here, a week ago, that's all," she said hastily. "He just … turned up in my classroom. I didn't believe it could be him, at first, but it was."

"No wonder you were so quick off the mark about Minerva having ulterior motives. Severus Snape, Severus Snape …"

"You won't see him on there," Hermione said.

Harry looked up from the map, green eyes shrewd behind his glasses. "You hid him in the Room of Requirement," he said, and it wasn't a question. "That's why I spotted you coming out from there tonight. Playing both ends of the Quidditch pitch, Hermione?"

"I wasn't going to tell him," Hermione said, unable to meet that steady gaze for long. She stared at the unlit fire, instead. "About the Room. Just about the Map, so he wouldn't be surprised when you found him. But he asked for my help — the only kind of help he'd let me give him."

"Alright," Harry said after a moment. He put his hand on her shoulder. "No harm done, in the long run, anyway. I blame him, for putting you in that position." With a final squeeze, he let go of her shoulder and tapped the map again. "Mischief managed. Come on, let's go."

"To the Room?" Hermione asked, and when Harry nodded, she shook her head. "Not tonight, Harry."

He looked at his watch. "It's not that late. You don't expect me to just go to bed and go quietly to sleep when I know that Severus Snape is alive and just upstairs, do you?"

"No, but …" Hermione bit her lip. "Look, like you've already guessed. Someone's cursed him. And it's … it's bad, tonight. He doesn't want to see you anyway, Harry, how do you think he'll take you hammering on his door when he's … ill?"

Harry frowned, and for a moment Hermione was going to ignore her and go charging up to the Room of Requirement anyway, in a replay of so many moments from their school days. Then, to her relief, he sighed, and flopped back down into the chair opposite hers. "You're probably right. How bad is it? The curse?"

"Remember Dumbledore's hand?" Hermione said, and he gave a shudder. "It looks like that, but here." She traced the place on her own left arm. "Right where the Dark Mark was."

Harry frowned. "Cursed through the Mark?"

"It is a Protean charm," Hermione said. "I was reading about their history again tonight, and Voldemort by no means invented them."

"He put his own special spin on them, though," Harry said wryly.

"Did he, though?" Hermione asked. "You knew him better than anyone, Harry. Except Professor Snape, maybe. He was powerful, and he was horrible, but how inventive was he?"

Harry gazed into space, expression thoughtful. "Not all that inventive, when you get down to it. I mean, he took things further than anyone else would have dared — seven Horcruxes, after all. Somewhat excessive. But apart from the flying … I can't think of a single spell he cast that wasn't something he could have learnt in the Library here." He frowned. "And you know, Professor Snape could do that as well, the flying. Maybe it was his spell, and he taught Tom Riddle. I mean, we know that Professor Snape was coming up with his own spells, and improving potions, even when he was a teenager." He looked back at Hermione. "Why does it matter?"

"We always talked about the Dark Marks as a way for Voldemort to signal to his followers, or them to signal to him," Hermione said. "But a Protean charm doesn't necessarily work that way. Look at the D.A. galleons — Neville and the others were using them to organise the resistance, and I didn't know, or need to know, anything about it. And it was my charm."

"That last day — Alecto Carrow used her Mark to tell Riddle she'd caught me," Harry said thoughtfully. "And Amycus came running in response. And Professor Snape." He paused. "Who was running to save me from them, I suppose, although I didn't know it at the time."

"So the Dark Marks worked like an ordinary Protean charm," Hermione said. "Change one, change all."

"Yes, but, Riddle's dead, and so is his magic." Harry touched his scar. "And he is dead, Hermione. Believe me, I'd know if he wasn't."

"Then there must be something different about the Dark Marks." Hermione bit her lip. "Maybe because they're Dark. Something residual."

"They left a scar," Harry said. "Did you find anything about that, in the Library?"

Hermione shook her head. "No. Other Protean charms either just stopped working — like parchments charmed to pass messages. But I haven't found anything else about someone putting a Protean charm on a tattoo, or a brand, magically-induced or otherwise." She picked at her thumbnail, thinking. "Harry — have you got any tattoos?"

"No! Why, do you?"

She shook her head, smiling. "No, but I went with Ginny when she had hers done — the Holyhead Harpies one. The point is, they bleed, when they're done, even when they're done magically. And there's magic in blood. "

"That's why I could come back, when Riddle killed me," Harry said. "Because my mother's magic was in my blood, which he'd taken."

"Right," Hermione said. "So when the Dark Marks were made … what if the witch or wizard's own magic was part of it, not just Voldemort's? The magic in their blood."

"Which is why there's still a trace of them, a scar!" Harry said. "Hermione, you're brilliant! That's it! Someone's worked out how to activate the remnants of the Protean charm in their Dark Mark scar!"

"Yes, but who?" Hermione said. "You said they're all dead, or in prison, or Malfoys."

"I'll Floo back to the Ministry first thing," Harry said.

"And tell them what? That Severus Snape is alive? He won't thank you," Hermione warned. "He won't thank you for knowing yourself. Telling Kingsley …" She shook her head. "I don't think he'd forgive it."

"I won't tell Kingsley anything," Harry said. "I'll tell him I've heard a rumour that there's a Death Eater unaccounted for, that's all. An anonymous tip, and I don't know if it's someone from the First Wizarding War who fled overseas and never came back, or someone who escaped us somehow, or whatever else." He grinned. "He won't ask why the tip came to the Boy Who Lived, you know, he'll just start an investigation."

"You're more comfortable with celebrity than you used to be," Hermione observed.

He grinned. "I'm dating the best Chaser the Holyhead Harpies have had for fifty years, I don't have much choice about it, do I?"

Hermione smiled back. She drew up her feet and hugged her knees. "I've missed you."

"I'm only ever a Floo away, you dimwit," Harry said.

She nodded. "I know. But, you know, we all got so busy, and then with my parents …"

He leaned forward and touched her foot gently. "Things still rough there?"

Hermione made herself smile. "No. A lot better, actually. But I don't think it'll ever be the same. My therapist says that I have to learn to understand the difference between the normal changes that happen when we grow up and the ones from … what I did."

"You mean saving their lives?" Harry asked. "Maybe they're the ones who should be in therapy, have you thought of that?"

"Yes," Hermione admitted. "And then I feel … disloyal."

Harry patted her foot and leaned back. "Sounds to me that that's what you should be working on."

Hermione shrugged. "Do you still have the nightmares?" she asked abruptly.

"Sometimes," he admitted softly. "It never happens … the way it really happened, in my dreams. Something goes wrong. I lose the Stone, and I can't find it, and I can't go on and face Riddle without it. Or I drop the vial with Professor Snape's memories on the way to the Pensieve, and I'm trying to carry them in my hands, and they keep spilling away. Stuff like that." He studied her. "You?"

"Sometimes," she echoed. "Always the same. Professor Snape. And in the dream, I know all the things we found out, that you told us — but I still don't help him, I just stand there and watch him die."

"You couldn't have saved him, Hermione," Harry said. "St Mungo's barely saved Arthur Weasley. You were an eighteen-year-old with first aid knowledge and a bottle of dittany."

"I know," she said softly. "But I didn't even try. He should have had someone try."

Harry snorted. "And it turns out he did, didn't he? Do you know how he did survive?"

"Fawkes," Hermione said succinctly.

"Of course." Harry smiled. "Good old Professor Dumbledore. He always had a loophole of some sort ready." He looked at his watch. "I've got to get back, I'm on first watch tonight." Standing, he held out his hand. "Come on, I'll walk you back to your rooms."

Hermione let him pull her to her feet, frowning. "I can walk across Hogwarts without an escort, Harry."

"If someone's playing around with Dark curses, we all need to be careful," Harry said seriously.

"Including you," Hermione pointed out.

Harry patted his robe. "Ah, but I'll be under the Cloak on the way back."

Hermione cancelled her spell, and unlocked the door. "What about the others?"

"Professor Sprout built a … sort of a granny flat, really, out by her place next to the greenhouses for Neville," Harry said. "It makes it more convenient to get up in the middle of the night when the mandrakes are teething, I suppose. I think he's safe enough with Pomona Sprout in shouting distance." He stuck his head out the door and looked up and down the corridor, and Hermione realised he had his wand at the ready. "Coast is clear, come on."

Hermione followed him towards the stairs. "And Ginny and Luna? Are you manly men going to stand guard over all of us?"

He gave a comically exaggerated grimace. "As much as it's going to pain me, I'm going to suggest Ginny and Luna share digs. That leaves just you without a room-mate, and if you could take care of me and Ron for all those months five years ago, I think you can take care of yourself. Add extra wards to your door, though, and don't wander around at night by yourself."

"Don't wander around at night alone?" Hermione said. She widened her eyes. "Who are you, and what have you done with Harry Potter?"

Harry grinned at her. "I didn't say not to wander around at night at all," he said. "Just exercise a bit of caution, and take company."

"And I say again …" Hermione said dryly.

They reached her door, and Harry stopped her with a hand on her arm before she could open it. "Hermione … I'm going to have to tell the others. Not Kingsley, but the rest of us."

Hermione nodded. "I know. But … talk to … him first. And maybe to Minerva?"

He nodded, took out the Invisibility Cloak, slung it about his shoulders, and disappeared. "Night, Hermione."

"Night."

She heard his footsteps fading away, and turned back to her door. About to open it, she stopped. Had she heard …?

The sound came again and Hermione spun on her heel, whipping out her wand in one smooth movement. "Homenum Revelio!"