At dinner that evening, Snape was thoroughly angry at the world. Not a single dunderhead had successfully completed their potion. Even Granger had produced a weak Aging Potion because sweat droplets had fallen into the cauldron. It was doubtlessly Pansy’s or Draco’s fault, though he would never admit it.
Between classes, he had spent his spare time casting cooling charms on ingredients that would lose their potency in the heat; at least he had done so to the ones he could salvage. It would take time to buy more, and it would put his department over budget. He was frustrated and completely exhausted as he stabbed his London Broil.
Worse yet, Dumbledore had placed the Doctor in the stool next to himself. That was Snape’s seat. Even more annoyingly, he seemed to be hanging on the man’s every word.
“Oh, and the castle is marvelous,” the Doctor was saying. “It’s exactly like it was when I visited last time, down to the last detail.”
“Don’t you mean it is exactly like it was after you altered it?” asked Snape with a clipped tone.
“I’m sorry, Professor,” said the Doctor, looking at Snape. “I don’t catch your meaning.”
“It’s fascinating,” said Snape, “How your arrival coincides with the worst heat wave in recent memory down in the dungeon.
“Severus, I am sure it has nothing to do with the Doctor,” said Dumbledore.
“No, wait, you say that the dungeons are unusually hot,” inquired the Doctor.
“I'm so happy to know that Hogwarts still employs the best and brightest,” Snape shot back.
“Where does the heat seem to be coming from-the walls, the floor?” asked the Doctor.
Snape glared at the man, trying to figure out if he was attempting to mock him. The Doctor seemed genuinely concerned. 'How nice,' Snape thought bitterly.
“If you must know, if the floors get any hotter, students may be exiting the dungeons in their sock feet because their shoes will have melted to the floor,” Snape replied.
For a moment, the doctor’s eyes goggled, and then he looked worried. “Headmaster,” he asked. “May I have a tour of the dungeons after the evening meal?”
'NO,' yelled Snape mentally.
“I think that can be arranged. Severus, would you mind doing the honors?” asked Dumbledore with a stern expression.
“Of course not, Headmaster,” Severus replied with his usual reserve.
“This way,” Snape said as he led the Doctor to the dungeons.
The doctor removed what looked to Snape like a long, silver wand with a disk on top. The disk had a window on it that displayed numbers and letters. There was a button on the side.
“What is that?” Snape inquired suspiciously.
“A thermometer,” said the Doctor, bug-eyed and smiling. “I’m sure you Wizards use these too?”
“Yes, but not ones like that. You do realize that Muggle devices do not work here at Hogwarts?” Snape asked contemptuously.
“Ahh, but this is not Muggle. It’s Gallifreyan. I designed it myself,” the Doctor answered, still smiling annoyingly.
“Alien,” spat Snape.
“I’ve been to a number of planets where you would be considered just as alien-and a freak. Not just Earth,” replied the Doctor.
Snape stopped and whipped his head in the Doctor’s direction, glaring.
Ignoring him, the Doctor took the temperature along the walls and the floor. “27 degrees, 28 degrees, 29 degrees-most certainly unusually hot, but not deadly,” said the Doctor, crouching and looking at his thermometer.
“Try working in it,” the professor growled, narrowing his eyes at the other man.
“And the temperature gets higher the further down I read. That’s odd, because warm air rises. “Professor, is there any spot down here where the floor is lower than any other?”
They stood looking at each other, the Doctor expectantly, Snape unwilling to reveal anything. After a long pause the Doctor spoke.
"Well?”
“Yes,” answered Snape reluctantly.
“May I see it?” asked the Doctor.
Snape had an unreadable expression on his face as his mind worked. He could simply refuse, but his boss would certainly hear about it. He said simply, “Follow me.”
With a flourish of his robes, the Potions Master led the way, walking with his usual swift pace. The Doctor, for a moment taken aback, caught up easily. Snape walked faster. The Doctor walked faster. Snape and the Doctor kept increasing their speed until they were running at a swift pace. They nearly ran into two Ravenclaws.
“And we’d lose House points if we tried that,” said one to the other.
Snape stopped abruptly. The Doctor stopped just as abruptly, disappointing Snape.
“The dungeons are quite large. You were wise to move quickly, otherwise the trip might have taken all night,” said the Doctor cheerfully.
Snape scowled as he took the wards off and opened a door to his right.
“This is the storeroom for the school’s potions ingredients. Do NOT touch anything,” he warned the Doctor.
Snape led the other man into the middle of the room. Here, Snape took the wards off a trap door and grabbed the handle after performing a Cooling Charm on it.
“This chamber was designed to store particularly climate-sensitive potions ingredients. Of course, I have had to remove its contents, most of which were completely destroyed by the heat,” Snape said.
When he opened the door, the hot air hit them like a blast furnace. Snape moved aside as the Doctor descended into the hole.
Snape considered closing and sealing the trapdoor with the Doctor inside. If the man was so powerful, he could make his way out.
The Doctor’s voice drifted up from the cellar, “Unless you have two hearts and a bypass respiratory system, I suggest you not try that.” Snape stepped back, startled. Was this Doctor a Legilimens?
After a few minutes, the Doctor ascended the steps. “Thirty-eight degrees. Curious. The heat source is a strong one, and it’s definitely underground. Are there any caves, tunnels, or chambers under the school?” he asked.
“There is the Chamber of Secrets, but we sealed it five years ago, after a student was abducted and taken down into it,” said Snape.
“I need to see this chamber. Is there any way to get down there?” asked the Doctor.
“I suggest you consult the Headmaster,” answered Snape.
Meanwhile, the whole school seemed to know the Doctor’s diagnosis of the problem. Something was in the Chamber of Secrets, producing terrible heat. Several Slytherins made snide comments to Potter about not finishing the job during his second year. Others thought Voldemort must be hiding down there again, and that he placed some kind of temperature hex on the school from below. Several became worried that the whole school would explode or burn down. Frantic parents sent the Headmaster owls suggesting that he close the school and send their children home.
Snape moved his classes out of the dungeons to a first-floor classroom. Slytherin House was relocated temporarily to another location, an action not well received among its members. Some people were looking to Harry for help; others were blaming him for the entire business.
That night, Harry had had enough.
“I’m going down there,” he said. “If Voldemort is back, I’m the one who can kill him.”
“I’m going with you,” said Ron.
“And me too,” said Hermione.
“No, you’ll only get hurt,” said Harry bravely.
“What about you? You need back-up,” said Ron.
“And what if you need a spell you don’t know?” asked Hermione in all seriousness. “You don’t even know how to do a Cooling Charm.”
Harry looked at his friends. Sadly, reluctantly, he relented. Harry threw on his Invisibility Cloak, and Hermione cast a Disillusionment charm Ron and herself.
They had to pass the Defence Against the Dark Arts classroom on the way to the dungeon stairs, and as they did, the Doctor stepped out of it and called, “You three. In here. Now.”