Disclaimer: The characters here and the world they inhabit are the creation and property of JK Rowling and her assigns.
Septima realized that Severus was avoiding her. He allowed one night per week for discussing research, but he always made sure it was a night when one or both of them had early classes the next morning. He kept the conversations professional and avoided too much animation even then.
Occasionally during lulls in their discussion, she looked at him and remembered her picture of Decartes. Shortly afterward she would find herself thinking about their early days. Sometimes it was her pregnancy, and sometimes it was her hospital stay. She would come back to herself and see him looking intently at her. Was he trying to see into her mind? She didn't ask, not wanting to start an argument, but she didn't want to constantly think about it. She started hiding her eyes from him. Maybe he enjoyed torturing himself with the what-ifs of their life, but she couldn't take it.
Although many were worried about the Chamber of Secrets and whatever had caused Mrs. Norris to petrify, the true plague in Septima's life was Gilderoy Lockhart. For some reason he had fastened on to her in the early days when he wanted a guide around the school. She had shown him around, making non-committal replies to his self-aggrandizing advances. At dinner she was forced to endure the amused look that came from beneath Severus's raised eyebrow.
She tried to turn Gilderoy onto Aurora, but that professor smilingly admitted to being already attached to another wizard. She tried to turn him toward Sibyll, Poppy, or anyone, but he shook his head. “They're too busy with unimportant matters. I can't be bothered with those things, and you're a good listener.”
He started asking for long walks on the grounds. She retreated into her own mind, imagining that she was discussing research with Severus. When finally left to herself, she dashed back to her rooms and captured her thoughts in her notebooks.
When a student was petrified, Septima was almost grateful to be asked to consult on the case. She was summoned to the Hospital Wing to take a good look at the child, who looked hardly old enough to even be a student. “He's so little and helpless!”
Minerva's lip twisted. “He's small for his age, but he has the true heart of a lion.”
Gryffindor, then. “Oh, I'm sorry. I meant, he seems helpless.”
Severus stepped close. “We need to know what's causing this. Do you think Arithmancy might tell us?”
“I can try.” She got information about the boy and his habits and went back to her office. Severus followed.
“Is there anything I can do to help?”
“Tell me about him.”
Severus told her about a boy who would touch any ingredient no matter how vile but who was an indifferent brewer. Septima looked at the terms she had sketched and added one for the stony nature of the child now. She added one each for the expressions “Chamber of Secrets” and “Heir of Slytherin.” The terms started to move around in her head, and she made adjustments to her parchment. She took her wand out and tapped the runes as she usually did.
The terms started to move on the parchment, and she found that she couldn't move her wand away. For several minutes she felt magic flowing from her as the runes swirled and formed new patterns. Something sinister moved through her, something that frightened her. She looked up at Severus.
“Stop it,” he said, but all she could do was shake her head. The magic was having its way with her. Severus took out his own wand. “Finite Incantatem!” Septima remained trapped as the magic simply intensified.
Finally the parchment shook itself, and the runes settled as Septima's wand finally yielded to her will. She stood up and stepped away from her desk. “I've never had something like that happen in my life.”
Severus came around the desk and stood next to her. “Are you all right?”
“I think so.”
They had been looking at each other and now looked at the parchment. There was clearly some sort of organization to it; the runes were in rows and aligned perfectly. Yet there was no way to interpret it. Where Septima had put standard terms for the information she started with, there were now squiggles and curves.
“What's happened?” he asked.
“It must be another language.”
They stared at the serpentine marks, amazed at the way they seemed to be made by bold pen strokes. Septima's own hand was quite different, more economical. Severus tilted his head. “This rune is very similar to a pattern in the fireplace in the Slytherin common room.”
“Another language... that looks almost like snakes... do you suppose it's—”
They both said it at the same time. “Parseltongue.”
“Can you read it?” she asked.
He shook his head. “I can only understand a certain amount of it, as I can understand any language through Legilimency. For that I need some sort of eye-to-eye contact with the speaker.”
“Do you suppose Dumbledore can read it, then?”
Severus picked up the parchment. “I'll ask him.”
* * * * *
Over the next weeks, Septima worked on the materials side of the question, trying to calculate how the flesh of a living thing would turn to stone and what sorts of spells or potions might reverse the process. Another student was petrified and the atmosphere of the school became tense. The answers were sometimes confusing, and the ones that made sense all required the Mandrakes.
One night, Severus asked her to turn her attention to figuring out who might be injured next. “You know that no self-respecting Arithmancer meddles in the art that way,” she answered.
“You've done it before. Please, for me?”
She sighed and took out fresh parchment. She put her runes down and made her adjustments. She tapped it with her wand and watched as the terms arranged and rearranged themselves. They settled down somewhat quickly. What she saw mystified her. It couldn't be—it simply wasn't so. Septima looked up at Severus and shook her head. “It's no good. I must have done something wrong.”
She looked at the equations again, searching for her error. She found none, yet the result was impossible. Unable to face what made no sense, she ran from the room.
A/N: I'm very grateful to Trickie Woo for beta reading.