"A Logic Puzzle"

Disclaimer: The author claims no intellectual property rights of any kind to characters, plot points, or other ideas appearing in this work which originated in the Harry Potter novels by J.K. Rowling. The author receives no financial benefit from the use of these ideas and has written this work for personal amusement only.

Author's Note: I am not a particularly talented writer of fiction, and this is no great work of literature. It is merely an exploration of one of many plot points which severely irritated me in the canon. I hope the reader finds something to enjoy, and would appreciate any feedback.

Summary: One-shot. Professors Snape and Dumbledore test the defences of the Philosopher's Stone. No pairings.

"Severus," said Albus Dumbledore after the conclusion of a Hogwarts staff meeting, "how much progress have you made on your share of the security for the Philosopher's Stone?"

"Actually, it is complete as of this morning," drawled Snape in reply. "Would you care for a demonstration?"

Dumbledore assented, and Snape led him to the third-floor corridor which had been set aside for this purpose. They descended beneath the trapdoor (Snape wondered idly what on earth the architects had been thinking to have included such a chamber in the first place), some of which were still empty while the remainder contained currently deactivated traps designed by other faculty members, and stopped before the second-to-last chamber. Snape raised a hand, wordlessly signalling a halt to the other wizard, drew his wand, and silently made several complex gestures.

"I've activated it. Shall we?"

Dumbledore nodded and strode into the room. Such reckless overconfidence, Snape thought with a quiet snort. Bloody Gryffindor. He shook his head resignedly and followed.

Immediately upon their crossing the threshold, blue flames sprang up behind them to seal off a retreat, and black flames rose up to block the way forward. Against the wall to their left was a small stone shelf, upon which sat seven bottles of various shapes and sizes, and a furled parchment scroll tied loosely with string.

"Have fun, Albus," Snape deadpanned. "Let's see how you do." This ought to be amusing, he thought to himself.

The aged wizard studied the flames from several angles at first, wand in hand. He nodded in satisfaction after a brief moment, seemingly satisfied that he would not, in fact, be able to dispel them. He paused a moment, then raised his wand and cast a nonverbal Aguamenti, nodding again when the jet of water evaporated before reaching the flames. Snape snickered in the background.

Dumbledore turned away from the flames and regarded the shelf; after checking the scroll for curses (Severus had actually toyed with the idea of cursing the scroll at one point, but eventually decided against it in favour of a more interesting alternative), he untied and unfurled it, then looked at his companion quizzically.

"A riddle, Severus?" he asked, sounding amused.

"It's a logic puzzle," replied the other wizard disdainfully. "Living in Wizarding culture for any length of time is the surest way to eradicate one's logical reasoning skills; surely you in particular can see that? I assure you, it is not intractable," he sneered.

Dumbledore just smiled, shook his head, and returned to the scroll. Eventually he conjured a blank piece of parchment and a quill, and began drawing charts and making copious notes; Snape smirked behind his back.

Eventually the older man looked up. "I've got it. This one," he said, indicating the smallest bottle, "will take me forward, and this –" he indicated another, "will take me back. Shall I take a drink?" he asked.

"Only if you want to die," Snape replied in a deadpan tone.

"I am quite certain I have solved the riddle, Severus, and these are the bottles it indicates," said Dumbledore with just a hint of confused exasperation.

"I do not dispute that. However, as I told you, Albus, this is a logic puzzle. Think!" When Dumbledore did not reply and merely cocked his head, Snape sighed and continued. "They're all poison, Albus," he said snidely. "Isn't it obvious? It would be completely illogical to provide the solution when we want to keep the intruders out, wouldn't you say? The riddle is a red herring. The only way to bypass the flames is to be the caster or to possess a wand which they are charmed to recognise. Only I and the Flamels are able to pass through." Snape had not yet added Dumbledore's wand to the list, specifically for the purpose of this test.

"That will not do, Severus. Why not keep the riddle as is, but use the correct potions?"

"You asked me to design security, Albus, not a bloody obstacle course! It sounds to me as though you want somebody to get in!"

"Perhaps I do, Severus. I have no intention of disclosing all of my plans. I assume you do have the potions you'd need?"

"I can brew them," Snape replied with no little reluctance. "Are you certain, Albus?"

"Absolutely certain," he said cheerfully. "Now, can you get us out of here?"

"Of course," he said dryly, making a brief wand motion; the flames dwindled and sank into the floor. "I still say you're making a mistake, but I'll replace the potions this evening."

"Good, good," Dumbledore replied absently as they began to retrace their steps.

Once they were back at the trapdoor, Dumbledore summoned a broomstick and flew out. Snape watched him go with a wry chuckle, then made his own ascent unaided once the Headmaster was out of sight.

I'll do as he asks, Snape thought bitterly, remembering the oath of allegiance he had sworn, but Albus Dumbledore is an excellent candidate for the poster-boy of Wizarding irrationality. With friends like these, who needs enemies?