Minerva groaned as she heard a knock on the door to the staff room. She really did not need visitors right now. In fact, if everything had gone well, it would have been rather dangerous for them to be here. But her attempt at the spell had been a disaster. She had started it that morning, expecting that from that point on, everything would be fairly easy. An enormous amount of heat would be created by the spell, enough to satiate the ghosts' absorption capacity, and then, gradually, it would be reduced to an agreeable temperature that could keep the ghosts' energy level constant at the same time. The initial heat would keep her busy for a few days, checking on the castle and its furniture, as there was a risk that some things would catch fire, even with all the heat-repelling charms she had cast. She herself had pulled on a protective overall of dragon hide.
But it had been no use. The first time, she thought she had pronounced part of the spell wrong, unfamiliar as it was. But after the second and third time it had struck her what had really happened: the spell had worked, but only for a few seconds. Then it had reached the ghosts and all of the warmth had been absorbed instantly.
Her plan had failed.
"Come in," she said with a sigh, looking up at the door.
"Good afternoon, Professor," Hermione Granger said as she came in, followed by Ginny Weasley. "Lavender told us that it was still safe to enter the castle, so I hope we don't disturb you…"
"No, it's fine, Miss Granger," Minerva said. "May I ask why you are here?"
"We were in Hogsmeade," Ginny said. "Picking up Harry's Christmas present. And we just figured we'd come by and see if there was anything we could do to help. With the spell or… anything…"
Minerva looked at them for a moment, thinking. Both girls were talented and Miss Weasley had been known to cast her charms slightly too forcefully at times… "I know I said that I did not need help," she said slowly, "but actually I am very glad to see you two."
Hermione beamed, clearly delighted at the prospect of helping out.
Yet by the time Minerva had finished explaining what had happened that morning, even Hermione was frowning.
"Have you found an alternative spell?" she asked.
Minerva shook her head. "Not yet. But perhaps, thanks to you two, that won't be necessary. I think that, if we would attempt to cast it simultaneously among the three of us, there is indeed a good chance we would succeed."
"Yes," Ginny said. "That does make sense. But what would work best? If we cast it together at the centre of the castle, or spread out to different corners?"
Minerva gave her a thin smile. "Good thinking, Miss Weasley. It would probably be better if we do spread out. But first you need these." She waved her wand and two more dragon hide overalls appeared.
…
This time, a spark of heat could indeed be felt, lasting almost a whole minute after the spell was cast. Unfortunately, that wasn't enough, and Minerva felt rather defeated when she returned to the staffroom, where the girls were waiting. Of course she would find an alternative in time, but this set them back at least a couple of days. There would be no chance to return earlier for those to whom Hogwarts was the only home.
Hermione was biting her lip. "Is there anything else we can do to make it stronger, Professor?" she asked as soon as she saw Minerva. "We could bring more people…"
"At this rate, we would need more than the whole school," Minerva sighed. "We have to select another option, I'm afraid. Or rather, I have to."
"If there is anything we can do, please, do not hesitate to ask, Professor," Ginny said.
"I would, Miss Weasley," Minerva said, "but I don't doubt that Miss Granger has already read every book on the subject available to the students since the problem became known." She gave Hermione a small smile. "So if you have any new suggestions, I am ready to listen, but other than that there is little to do right now."
"I doubt I will know any spells that you haven't thought of yet, Professor," Hermione said modestly, blushing a little.
"Then I will send you home once again," Minerva said, nodding at her. "But don't worry. I will get this under control."