On the last day of November, the sky was an oppressive leaden gray. The air was damp and cold, white mist spilling from every breath, while the torches in the castle corridors seemed to flicker more unsteadily than usual. An invisible sense of agitation, like low atmospheric pressure, weighed on some students' hearts—especially those sensitive to astronomy or well aware of certain cyclical changes.
All day, Snape had been even quieter than usual, the oppressive air around him nearly freezing solid. Even in Potions class, he merely went through the motions, responding coldly to Professor Slughorn's praise. His gaze occasionally swept sharply over the Gryffindor table, lingering particularly on Remus Lupin. Lupin's complexion was an unnatural waxy yellow today, and his fingers sometimes trembled faintly beyond his control. Still, he tried to maintain a calm facade, laughing and chatting with Potter and Black beside him, though his smile looked somewhat forced.
Through the contract, Lin Yanqing could clearly sense the emotions within Snape: a mixture of the desire for confirmation, vengeful satisfaction, and intense vigilance, like a volcano on the verge of eruption, forcibly suppressed beneath a cold exterior. He knew that the moment Snape had been waiting to "observe" would come tonight.
After afternoon classes ended, Snape neither went to the library nor returned to the dungeon common room. Like a black phantom, he silently blended into the castle's tangled shadows. Lin Yanqing tried to vaguely sense his location through the contract, but could only determine that he was moving toward some secluded corner of the castle—most likely somewhere with a view of the path leading to the Whomping Willow.
At dinner, Snape did not appear in the Great Hall. Sitting at the Ravenclaw table, Lin Yanqing had no appetite. From the other end of the contract, he could sense the extreme focus and cold excitement of someone lying in wait. Snape had already begun to act.
"Ding-dong! (⊙﹏⊙) The contract target has left the normal activity area and entered high-risk monitoring status! Emergency side quest triggered—[Shadow Watch]!" Quest Description: On the night of the full moon, danger lurks everywhere! The contract target is carrying out high-risk actions alone. As the system-bound perfect partner, how could the host simply stand by? Quest Requirement: Ensure the safety of contract target Snape during this full-moon operation and prevent him from suffering irreversible, severe injury. Quest Reward: Concealment Charm (single-use; can distort the trajectory of one fatal attack) x1, System Points +100. Failure Penalty: The contract target will randomly receive the debuff [A week of bad luck] or [Slight blockage of magic circulation]. (＞﹏＜)
Lin Yanqing's grip on his fork tightened. The system quest confirmed his unease. Snape had indeed gone there, and the system had judged this trip to carry a "fatal" risk.
"Kiddo, can you pinpoint his exact location?" he asked urgently in his mind.
"Um... the signal is being heavily disrupted by magic. It's probably the ancient warding around the Whomping Willow! (;′д｀)ゞ" The system popped up a magical mirror emoji with an empty signal bar. "I can only determine the general direction, about the same as what the host can sense!"
He could not wait any longer. Lin Yanqing swiftly and inconspicuously left the Great Hall. He did not try to follow Snape—that would have been too easy to detect, and far too dangerous. Instead, he chose a more roundabout, perhaps more effective method.
He hurried to the Owlery and sent out a brief coded note addressed to "S.S." (Severus Snape). It reminded him to check whether the constant-humidity ward around a certain "experimental sample" had malfunctioned—an issue they had previously discussed regarding Thestral tail feather powder. It was a reasonable excuse for contact that would not arouse outsiders' suspicions. He hoped the school owl's magical tracking would temporarily interrupt Snape's actions, or at least distract him enough to make him more alert.
Afterward, he went to the Seventh Floor and entered the Room of Requirement. That night, in response to his needs, the room became a monitoring chamber containing an enormous magical water mirror capable of displaying blurry images of a specific area. Mist swirled across the mirror's surface, allowing him to make out only the outline of the castle grounds and the Whomping Willow area, not any individual figures. Still, that was enough to monitor whether any major disturbance occurred there.
Time passed second by second, each one exceptionally long. The image in the water mirror remained blurry, while the emotions at the other end of the contract stayed in a state of intense, dangerous concentration. Lin Yanqing could sense that Snape was approaching some core secret. His curiosity and desire for revenge were being greatly satisfied, but the accompanying danger was also rising exponentially.
Meanwhile, in the shadows near the Whomping Willow on the castle grounds.
Snape seemed to melt into the night, pressed close against the cold stone wall as his eyes locked onto the enormous willow tree thrashing wildly in the distance. He saw Potter, Black, and that little rat Peter sneaking closer. Then, somehow, they made the violent Whomping Willow freeze instantly. Immediately afterward, Lupin, dressed in ill-fitting clothes and clearly in a bad state, followed them into a hidden opening near the tree roots.
Just as he thought! They had a secret passage! Lupin's "illness" was absolutely connected to wherever that passage led!
A surge of ecstatic certainty and cold fury at finally having something on them rose within Snape. He nearly could not stop himself from rushing out and exposing them on the spot. But the remnants of his reason told him that this was not the time. He needed more conclusive evidence. He needed to know what lay at the other end of that passage.
He stood like a statue in the cold wind, waiting patiently and calculating the time. He wanted to know how long they would take to come out—or what exactly would happen inside.
Just then, a school owl flapped its wings as it precisely found the patch of shadow where he was hiding and dropped a note before him.
Snape frowned and picked it up impatiently. It was Lin Yanqing's handwriting, about the constant-humidity ward around an experimental sample? At such a crucial moment?
His first reaction was anger. He thought it had interrupted his important "observation." But the next second, he keenly sensed that something was wrong. Lin Yanqing knew he was carrying out an important "observation." Unless it was an extremely urgent and relevant matter, he would not have contacted him this way.
"Constant-humidity ward malfunction..." he muttered, his mind racing. Was it a warning? Had something gone wrong in the laboratory? Or was this itself a veiled reminder, warning him that the environment—his situation—had changed and that he needed to be vigilant?
He abruptly looked up at the deep, dark opening again. The unexpected note rang an alarm in his mind. He temporarily abandoned his plan to move closer. Growing more cautious, he concealed himself even deeper and continued his surveillance with sharper eyes, like the most patient of hunters.
What he did not know was that the note, which appeared to concern an experiment, had indeed worked. Like a drop of cold water, it briefly sobered the mind clouded by revenge and curiosity, preventing him from rashly stepping into that passage that might have led to a werewolf's den.
Inside the Room of Requirement, Lin Yanqing saw no major movement in the water mirror. Snape's emotions at the other end of the contract remained tense, but there were no violent waves of panic or pain, and Lin Yanqing let out a slight breath of relief. The notification that the quest was complete had not appeared, which meant the danger had not yet passed.
Not until late at night, when the moonlight was at its brightest, did Snape see Potter and the others helping Lupin out of the opening. Lupin was nearly collapsed, his face white as paper, and they quickly disappeared into the night.
He had obtained the "evidence" he wanted. Although he had not personally seen what lay at the end of the passage, Lupin's condition and the secret passage itself already explained a great deal. With a cold, satisfied sense of victory, he prepared to leave.
However, when he turned and moved through the shadows along his route back to the castle, he failed to notice a pair of eyes that belonged neither to the Marauders nor to Lin Yanqing. Filled with malice and mockery, they had spotted him—the "lone shadow beneath the moon"—from behind a castle window high above.
Snape believed his actions that night had been flawless, never realizing that he had already fallen under another, far more dangerous gaze.
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