"I've been working under the theory that the tattoo's boundary at the Manor had to do with the boundary of the property itself. Seeing as the Manor is something you own by birth, the blood boundary is already in effect. It's the only thing that makes sense. But Edinburgh is not a property you own."

He scratched his forehead, trying to follow. "Alright…"

"What I mean to say is, the Manor is tied to you by blood already. So it would make sense that the tattoo could work in tandem with that blood magic." She brushed back a stray curl impatiently. "But then why would it work similarly at Edinburgh."

She dropped her head into her hands, rubbing her temples. She heard the snap of a book closing.

"Because I spilled blood at Edinburgh. We all did."

Her head jerked up to him. He was staring at her with intense eyes.

"You what?"

"At the first ceremony," he said. "About a week after the Auction. When Edinburgh was opened to us, the Death Eaters had a celebration. Just us." His words poured quickly from his lips. "We were to enhance the wards on the castle by spilling blood and casting protection charms. The Dark Lord made it very clear that Edinburgh belonged to his loyal followers. It was our castle—"

"So then it follows," Hermione picked up, jumping out of her chair, "that the deed of Edinburgh—"

"—is in the name of every Death Eater who's ritually spilled their own blood there."

"Where do initiation ceremonies take place for new Death Eaters—?"

"At Edinburgh. With blood."

She slammed her book down on the table, punctuating the end of their thoughts. She was breathing hard with the joy of solving a riddle, and even though it was less than half the battle, she felt like she'd unlocked a chamber in her own mind.

"There is no separate barrier created. The 'barrier' represents the estate line. That's one less significant problem to worry about." She grinned, and her stomach fluttered as he smiled back at her. She could kiss him, if he'd accept it.

Pop!

"Master Draco!"

Hermione jumped. Mippy stood at her knee.

"Master Draco has guests!"

Draco frowned at the elf. "What guests?"

"Guests is coming to the library now!"

Hermione jumped, grabbing Nott Sr.'s book and her notes as Draco waved his wand to close the open books. She turned to ask Mippy to Apparate her upstairs just when the library doors flung open.

Hermione went still as Narcissa led in two people she had never seen before. "Draco, dear," said Narcissa, her eyes polite but strained. "Look who's paid a call to see us."

Hermione pressed herself back against the stacks, shoving the book and her notes between two larger texts.

She blinked at the two guests: an older gentleman with sparse facial hair, and a young woman, several years their senior. She had the brightest teeth Hermione had ever seen.

"Draco, you remember Professor Viktorov."

Draco stepped forward at his mother's prompt, shaking the man's hand. "Sir, it's a pleasure. It's been far too long."