Disclaimer: The characters here and the world they inhabit are the creation and property of JK Rowling and her assigns.

As soon as he gave the werewolf his Wolfsbane on the night of the full moon, Severus put together his supplies. They included the few drops of potion he would need, along with the wine, glasses, and text that were his excuse for seeing her. Of course he did hope to discuss some amount of their research together, but this was the chance he had hoped for. This potion would allow him to map Septima's mind and unlock the memory that was so important to them both.

The first thing he discovered was that Septima would never love the werewolf. She was playing along and playing for time. He almost laughed when he found her memories of those two kisses. He was startled and a little pleased by her reflection that the shape of Lupin's mouth allowed her to think of him. He recalled the conversation he had with Lupin as he had finished brewing the Wolfsbane.

"She's so innocent, Severus. I don't think she's ever been with a man."

"Are you sure? For all you know, she's had a lover for years. Maybe she's even had his child."

"No, I would be able to tell if that was the case. Dumbledore said that she had fancied a wizard but that the situation was impossible. When I kissed her, I could tell that she was unsure. No, she knows nothing of what happens when a man loves her."

"And you're going to teach her?"

"I think I'm just the man to do it."

"You should stick to teaching her Defense. How is that going, anyway?"

He probed her memories, trying to go way back. He couldn't get anywhere near her pregnancy. Instead, he found himself reliving a night shortly after that Christmas. They had used the glass-lined cauldron to make a successful potion. Nick had been delighted with their results and had sent them to an expensive restaurant where he had an account. After eating very well, they had gone to Septima's apartment where Severus had made love to her on what seemed like every surface in the flat. Every time Severus had thought he had surely used himself up, she had smiled at him, and he had wanted her again.

This potion did the sort of thing he wanted, but not to the extent he needed it. He would have to look at the formula again and adjust it, probably many times. It was too bad that he couldn't ask Septima to look at it. With her help, he could probably figure it out within a matter of hours.

The next afternoon, Severus watched Septima at a meeting in the staff lounge. He couldn't help it after the erotic memories he had surreptitiously shared with her. Dumbledore droned on about ways to watch for Sirius Black and the importance of keeping the students away from the Dementors during Hogsmeade weekends. Septima doodled in a notebook in a way he recognized. There was a look in her eye as she caught his glance. She was close to figuring something out.

Dumbledore finally stopped talking. The professors filed out, but Septima walked over toward the chalkboard and started jotting her notes, working frantically, as if she couldn't get it out fast enough. Severus walked over and sat in Dumbledore's chair, leaning back and watching her work. Finally, she tapped the board with her wand and stepped back to watch the terms move into place. When nothing happened, she groaned.

"I didn't get it down fast enough, and now it's gone," she muttered.

He didn't look at her, just at the board. "I take it that this is for a potion to turn elements into gold?"

She sighed. "It's obvious, isn't it?"

"It is to me because I'm familiar with your work," he chuckled, "but someone else might not realize it, due to the glaring lack of gold in your terms."

She squealed and leaped back to the board, where she erased several terms and started scribbling again. She tapped the board with her wand and, as the terms started to move, she cast a spell to lock the door. She then knelt before him. Severus didn't realize what she was doing until his fingers were buried in her hair and he was groaning. His head slammed into the chair back, rubbing up and down as the rest of his body moved in the rhythm she evoked.

Suddenly he had to stop her. He tugged at her hair until she her head lifted up to face him. "Septima, what of Remus?"

"I don't belong to him, at least not yet. This is us, Severus. For some reason I woke up today, and I couldn't get this old, unsolved equation out of my mind. I had to work at it until I got it right or I lost it again. Since I got it right..."

"Since you got it right, let's do this right." He pulled her up and lifted her on the table. Her pleasure in her success gave her some innate passion that was infectious. He wanted to savor the moment, but the way she sighed and whispered his name was too much for him. Afterward, they stood at the edge of the table and stared at the finished equations. They slowly started to refasten each other's clothing.

"You still have that improbability factor to work out," he observed as he fastened the final hook under her chin.

"I'll get it. Once I get all of these other equations worked out to that point, I'm sure I'll be able to use them together to figure that factor out." She smoothed his robe over his shoulders.

He kissed her. "What are we to do, now? Shall we skip dinner and move on toward what we do best? You're hair's an awful mess, now."

She raised a hand to her head. "We can't. Dumbledore would... Oh, Severus, we can't."

He knew she was distressed because she clung to him, fitting her body to his. He tipped her chin up. "How can we not? How can we possibly stay apart? This table bears witness to what lies between us."

She turned and looked as he pointed out the Septima-shaped section that gleamed after its unconventional polishing. She giggled and pointed to the shiny spot on the headrest of the Headmaster's chair. Then she looked sad and shook her head. "He says it's better for you, and he's been so happy with me lately. How can I go against that?"

He crushed her close again, wishing he knew the words to change her mind and knowing it was useless. Her mind was made up and there was no way to change it at the moment. He would have to wait. Perhaps when she remembered everything...

At length she drew back and turned to unlock the door. "Tell Remus that I'll be down for dinner as soon as I copy this." She sighed and added, "I'd appreciate it if you didn't tell him—"

"He thinks you're a virgin."

"Does he? Well, I guess I'll have to avoid unicorn-hunting expeditions with him then." With a humorless laugh she picked up her notebook and started writing the equations that filled the chalkboard. Severus was dismissed.

A/N: Thanks to Owlbait for beta reading!

Portions of this chapter were inspired by a discussion with Sunny33. ;)