Blaise didn't ask why Hermione wanted a boggart farm. Hermione suspected he thought she wanted them for some sort of revenge plan, which she was content to let him think. To make the boggart farm, Blaise and Hermione spent an afternoon taking old cauldrons, putting them upside-down in empty classrooms close to the Potions classroom, and pushing out their raw magic into them, formless, just existing. Some of the old cauldrons had decayed enough to leave the inner coating splotchy, which let magic leak out of them, or eaten away to have visible holes. They were careful to only take the cauldrons that, while perhaps banged up or dented, were either pure metal or still fully-coated inside.

The decision to do this in the dungeons near the Potions classroom had been a practical one.

"People are most afraid of Professor Snape," Blaise had pointed out. "Hopefully, the sense of their fear and anxiety will creep out of the classroom and transform our magic into boggarts."

"Fingers crossed," Hermione said, the corner of her lips twitching up. "It's worth a try."

With the boggart farm left to grow, Hermione focused her coven on the next big thing for them: the blood debt ritual. They met one evening to discuss the particulars leading up to the ritual and get everything into place.

"The new moon is the eleventh," Hermione told them all. She frowned. "It'll be frigid outside. We might want to find a place to do this one inside."

"That is a bad idea," Susan said immediately. "We're anticipating pulling Sirius Black into our summoning circle. We should not drag him into the castle."

Hermione paused. "…that's a really good point."

"I forgot to ask Ron and Neville about blood," Harry admitted, wincing. "I'll do it soon."

"That's crucial," Hermione reminded him. "Without virgin blood, we can't do the ritual at all."

"I know, I know," Harry said. "I just forgot."

"Do we have a plan of what to do after the ritual?" Blaise asked, raising an eyebrow. "If it works, we'll have Sirius Black trapped in a ritual circle. That's not exactly 'normal'."

"I imagine we'd owl the Ministry," Susan said, biting her lip. "Or should we just go to Dumbledore?"

"We could offer him cheese and crackers," Luna said. "I bet he'd be hungry."

Harry looked at Luna sideways, but she seemed perfectly serious.

"I would normally say 'get Snape', as he'd be the closest, but that seems like a bad idea, given his history with Sirius Black," Hermione said with a sigh. "Dumbledore is probably our best bet."

"Wait," said Blaise. He looked at her funny. "What history between Snape and Black?"

"They were in school together," Harry said. "Lupin and Black were friends with my dad, and Snape hates Lupin, and he hated my dad, so we figure he hates Black as well."

"Should we have an owl on hand, then, to send to Dumbledore?" Susan asked. "Or should one of us run and get him?"

"Probably an owl," Hermione said decisively. "We don't know how hard it will be to hold a circle around Black. We might need all of our power together."

"I can make sure we have a couple owls around," Luna said. "Do we want Harry's owl specifically?"

"Wouldn't hurt," Harry said. "Hedwig tends to stand out."

"That's the plan, then," Hermione said. "Do we want to do this before curfew? Dusk is around five o'clock, so we could get this done before curfew."

"Yes," Susan said decisively. "We're going to be in enough trouble for catching Sirius Black. The last thing we need is points docked for being out after hours. We can do it after dinner."

"Hang on." Blaise looked around at them all. "Are we sure we want to just go to the teachers?"

They all turned to look at him in surprise. Blaise shrugged.

"Well, it's just – this is Potter's ritual, isn't it?" Blaise said. "Calling in the blood debt owed to his family. Does Harry want Sirius Black arrested. Or…"

He trailed off, shrugging again, his eyes looking at Harry. Harry looked uncomfortable.

"Probably," Harry said, after a long pause. "We—we'll be prepared to owl Dumbledore once we capture him, but… we'll wait and see how it all goes." He looked determined, and his voice hardened. "I have some questions I want him to answer, first."

After they'd worked out a rough plan for Tuesday night, Luna held Hermione back as they all went their separate ways.

"Did you like your present?" Luna asked, rolling onto the balls of her feet and back again. "Your map?"

"Oh! I—I don't know what it's of," Hermione admitted. "I mean, I can see that it's the UK and Ireland, but I don't know what the red lines are."

Luna tilted her head. "You don't?"

"How am I supposed to?" Hermione said, astonished. "There's just a few of them. They look like blood vessels, going all over the place."

Luna looked amused. "Did you find Hogwarts?"

"No," Hermione said pointedly. "It was difficult to figure out where it would even be, there were so many red lines crossing… it…"

She trailed off, her eyes going wide with realization.

Luna grinned.

"How did you get such a thing?" Hermione demanded, astonished. "If it's really what I think it is…"

"Oh, we had one around." Luna shrugged. "It's a copy of a Lovegood map. We have a fair number of things like this."

Luna's tone was airy, dismissive, but Hermione could tell Luna was a bit touchy on the topic, so she didn't press.

"I thought it'd be helpful," Luna said, happy. "Even though I'm not supposed to know anything, I know."

"Helpful?" Hermione asked. "For what?"

Luna's eyes gleamed.

"One of the red lines travels up north out over the water, all the way to Norway," she remarked. "Did you notice?"

"I didn't…" Hermione said slowly.

"Oh," Luna said, her tone innocent. "Maybe you should look over it again."

After they parted ways, Hermione immediately went to her room and dug out Luna's map, unrolling it on her bed, her eyes scanning it over.

"So Hogwarts must be here," Hermione muttered to herself. "That one's easy – it's got the most ley lines. So this must be Stonehenge… it's in about the right spot…"

Luna's hint had helped – Hermione was able to see ley lines running past or through major wizarding landmarks – Diagon Alley, Hogsmeade, the Ministry of Magic. Even St. Mungos was placed overtop of a nexus.

"Why does she think I care about Norway?" Hermione murmured, tracing the map with her finger. "It's got to be this one – there's only one going this direction, really…"

There was only one ley line that went northeast from Scotland. The line had a few curves and bumps, but it went nearly directly to Norway.

"There's nothing here," Hermione said, frustrated. "It just goes across the water. And I don't care about Norway. Does Luna think there's something on this map that's not there?"

Crookshanks came up next to Hermione, meowing and settling down next to her. Hermione absently stroked him as she looked at the map.

"This must be Hogwarts," she said again. "It's not labeled though. I know it's Hogwarts, though, because it's at the nexus of the ley lines. Hogsmeade is labeled, though. So why isn't Hogwarts…?"

Crookshanks butted her hand with his head, demanding more scratches. Hermione obliged while she studied the map.

"It's Unplottable," Hermione remembered, comprehension dawning. "So it can't be on the map – I only know it is because I know it's on a ley line nexus. So then…

Hermione's finger traced the ley line towards Norway, slowly traversing the North Sea. There was one small nexus in the middle of the ocean at a bit of a bump, two thin red lines crossing. There was nothing there, though, even though it was a nexus—

Just like Hogwarts wasn't there—

"Oh my god," Hermione breathed, her eyes going wide. "She's done it. She's done it."

She scrambled for Tom Riddle's diary, grabbing a self-inking quill.

I have it, she wrote excitedly. I have a way to get there.

How? Tom wrote back. No one but the Ministry knows where it is. It's been rendered Unplottable. And it's in the middle of the North Sea.

Hermione grinned viciously as she wrote back, feeling a sharp pleasure at knowing something magical that Tom Riddle didn't already know.

You'll just have to wait and see.