Undercurrents and Warmth Beneath the Ice

November at Hogwarts was wrapped in a damp, cold chill. The mist rising from the Black Lake never dispersed, and the castle's stone walls always felt cool to the touch. Ever since that subtle "stand together" on Halloween night, the relationship between Snape and Lin Yanqing had entered an extremely peculiar, yet remarkably stable, new phase.

The Marauders' harassment hadn't stopped, but their tactics seemed to have shifted again. They no longer engaged in minor actions that left obvious traces, opting instead for a more suffocating tactic of isolation. Whether in the corridors, the Great Hall, or the library, whenever Snape appeared, an invisible vacuum would instantly form around him, accompanied by deliberately hushed whispers and undisguised looks of rejection. Even some Slytherins, for reasons unknown, began to keep their distance from him.

Snape's response was to envelop himself in an even thicker layer of ice. He moved like a black, solitary island, his gaze colder than the air outside the castle. However, under this intense pressure, his collaboration with Lin Yanqing in the Room of Requirement laboratory became more intimate and... efficient than ever before.

Tonight, the laboratory was more chaotic than usual, but also more like a fully functional stronghold. In addition to the core operation console and instrument racks, there was even a small magical incubator in the corner, storing several highly temperature-sensitive active ingredients.

Snape was hunched over a complex filtration device made of crystal and mithril, his brow furrowed, performing one of the most critical steps in refining the Wolfsbane Potion: separating and purifying the calming components from the Moonpetal Flower extract while eliminating its accompanying neurotoxic substances. This process demanded extremely precise magical manipulation and near-obsessive stability; any slight error could lead to complete failure or even contamination of the materials.

Lin Yanqing stood half a step behind and to his side, monitoring a cauldron of Silverleaf Grass base liquid being slowly heated nearby, ready to hand over any auxiliary materials or stabilizers Snape might need. He held his breath, sensing through their contract the intensely focused and taut mental state emanating from Snape, like walking a tightrope high in the sky.

The experiment had been underway for two hours, progressing slowly. Fine beads of sweat dotted Snape's forehead. His right hand, controlling his wand, was steady as a machine, but his fingertips were slightly pale.

Suddenly, a faint blue light flickered uncontrollably within the filtration device, accompanied by an extremely subtle yet grating sound of magical friction. Snape's arm tensed instantly. The magical output from his wand tip was forcibly suppressed to a more refined setting, but his breathing faltered for a brief moment.

It was this momentary lapse that caused the precious liquid in the center of the device, glowing with a moon-like sheen, to develop an ominous cloudiness at its edges.

"Stabilizer three, ice crystal powder, 0.3 grams, now!" Snape's voice was hoarse, carrying an undeniable command, even a hint of urgency born from their previous successful cooperation that he himself didn't notice.

Almost as soon as he finished speaking, a small crystal dish containing the precisely measured ice crystal powder was smoothly placed within his reach. Lin Yanqing's movements were without hesitation.

Snape quickly used his free left hand to deposit the powder into a specific port on the device. A soft white light flashed, forcibly calming the agitated magic within the apparatus, and the liquid regained its clarity.

The crisis was averted.

Snape didn't immediately continue. He maintained his hunched posture for a few seconds before very slowly straightening up. He didn't look at Lin Yanqing, but the tension in his back eased slightly.

"Reaction speed, satisfactory," he stated drily, his voice returning to its usual coldness, as if the urgency of that moment had never existed.

Lin Yanqing said nothing, merely silently taking the used utensils to the sink nearby and beginning their preliminary cleaning with the Cleaning Charm. He knew that this "satisfactory" from Snape's lips was almost equivalent to fervent praise. It was an acknowledgment based on capability, more in line with their status as "conspirators" than any superficial thanks.

Silence descended once more, broken only by the hum of the instruments. Only after the core step was completed and Snape had carefully sealed the preliminary essence did the stifling atmosphere in the laboratory slightly dissipate.

He walked to the small table in the corner and picked up his mug—which had been refilled with hot tea. He took a large gulp, then, as if mentioning it casually, his gaze fell upon the bottles and jars of dangerous materials on the shelves.

"Lupin," he uttered the name, his voice somewhat muffled by the steam from the hot tea, "In Charms class this afternoon, Flitwick praised him for his 'returning state'."

Lin Yanqing's hand, wiping a utensil, paused slightly. He looked at Snape.

Snape's profile was indistinct in the dim green light, but in his dark eyes flashed the almost fanatical glint of a researcher, and a trace of... cold understanding.

"A brief period of calm before the full moon," Snape murmured, as if analyzing an interesting potion phenomenon. "A feigned 'normalcy' to conceal the impending 'abnormality.' A rather ingenious... biological instinct."

His words held no sympathy for the werewolf, only an exploration of the phenomenon's essence and the excitement of an impending revelation. He turned to Lin Yanqing, his gaze sharp.

"We need more data. The final live observation before the night of the full moon is crucial."

This meant he planned to monitor Lupin more closely, and possibly more dangerously, in the days leading up to the full moon. This decision itself signaled immense risk.

Lin Yanqing felt his heart tighten slightly. He put down the utensil he was holding and walked to the operation console, pointing to the filtration device that had nearly malfunctioned and the parchment beside it, which recorded complex data and calculation processes.

"The magic conduction efficiency of the device's third node is unstable. It could be insufficient mithril purity, or there might be minor flaws in the etched Ancient Runes internally. Before reaching this step next time, it would be best to conduct a stress test." His voice was calm, steering the conversation back to the specific technical challenges at hand, without directly responding to the dangerous "observation" plan, but instead pointing out the technical root of the recent risk.

Snape stared at the spot Lin Yanqing indicated, then looked at the data on the parchment. His brow furrowed again, and he fell into thought. After a long moment, he let out a cold snort, "Obvious. It seems some so-called 'top-tier alchemical equipment' is nothing but crudely made trash."

He didn't mention Lupin again, but Lin Yanqing knew he had heard him. The reminder about the device's potential flaws also applied to the more dangerous "live observation" plan—any minor oversight could lead to catastrophic consequences.

By the time they left the Room of Requirement, it was late at night. At the cold intersection, Snape, as usual, turned to leave first. But this time, before his figure disappeared, he left behind a short sentence that drifted on the wind, almost inaudible.

"...Next time, bring your mug."

Lin Yanqing stood frozen, then, an indescribable warmth quietly melted away the chill of Hogwarts' November night.

It wasn't an invitation, nor was it concern.

It was the confirmation of basic rules for resource (tea) sharing between "conspirators." It was extremely limited... logistical support given to a reliable ally who would provide crucial technical assistance in his impending dangerous actions.

Beneath the ice, though faint, the warmth was real. And outside the castle, the full moon was silently, steadily growing rounder.