Severus Snape moved through the cramped tunnel underneath the Whomping Willow. His mind flashed back to the conversation which had occurred on the 7th of August, 3 days ago, between him and Sirius Black and led to his discovery of the secret passage underneath the Willow...

"Oy, Snivellus!" shouted Sirius Black.

Severus Snape looked up from his book. "Yes, Black? What do you want? No, wait, I can guess. You want to pull some amusing-to-you prank involving my humiliation because I had the audacity to get sorted into Slytherin, which automatically means I'm up to my eyeballs in the Dark Arts."

Black grinned, then replied, "Not this time. You know Remus Lupin?"

Severus gained interest at the mention of Lupin. "The student who suffers from a mysterious illness that apparently forces him to vanish from the school grounds every month at the full moon?"

Black nodded. "The one and only! You want to find out why he vanishes every full moon?"

"Yes...?" replied Severus, uncertain of where this was going.

"Easy! Get a stick, and then go to the Whomping Willow-"

"No, I know enough, this is all just a huge setup to get the stuffing knocked out of me."

Black gave a look of fake shock. "What? No, I'm really telling the truth. There's a knot by the base of the tree. Poke that, and the whole thing freezes up."

"I don't believe you." replied Severus curtly.

Black gave an annoyed huff before picking up a stick. "Fine. I guess I'll just have to show you."

In reply, Severus pulled his wand on Black. "Just remember, I'll have this trained on you the whole time."

Black nodded, then walked towards the Whomping Willow, its branches swaying in the breeze. As the two of them neared closer, the tree began to rear its fist-like branches. Black bent down at the tree's base, and true to his word, Severus did indeed see a knot-like shape there. Black pressed it with his stick, and the tree stopped moving.

Severus glanced at it before asking, "When does it start moving again?"

Black responded, "It usually stays still for about ten minutes or so."

Severus gave a curt nod, then responded, "When is the next full moon?"

Black replied, "August 10th. About two weeks or so from now. Be ready, eh?"

And with that, he strode off towards the castle.

Severus had indeed followed Black's instructions to the letter. After seeing Madam Pomfrey escorting Lupin underneath the Willow, Severus had waited for it to start moving again before prodding the knot and opening the secret passage. He had crawled through the tunnel for nearly a half hour, but was now sure he was near the end, as he could make out the shape of a door. He heard a crunch behind him and looked around, but saw nothing. Dismissing it, he continued on, opened the door, and slipped through. Looking around at his surroundings, Severus realized exactly where it was.

He was in the Shrieking Shack.

X X X

Unbeknownst to Severus, Sirius Black had been following him as he walked through the passage, covered by James Potter's invisibility cloak. As soon as Severus had walked through the doorway, Black had hurried forward, slammed, and bolted the doorway. Hearing the door slam, Severus banged on it repeatedly, only to be responded with laughter he knew was Black's, followed by the sound of him running away.

"Severus?" a weak voice behind him called. He turned to see Remus Lupin. "What are you doing here?" asked Remus. "Black told me to come here." replied Severus. "He told me how to get into the secret passage by poking the Whomping Willow's knot."

Lupin's face drained of all color. "Oh no. Oh no. Oh no no no no. NO!" he cried out. "This is bad. This is very, very bad."

A wave of fear crossed Severus. "I presume this means... you are a werewolf?"

"Yes, and this is the worst time to be trapped in the Shrieking Shack, because it's full moon, and-"

But Lupin was cut off by a loud, terrible snarl. His head was lengthening, along with his whole body. Hair was sprouting wildly all over his body, as his hands began to curl into curled paws. His shoulders hunched, and finally his teeth became sharp and pointed.

The werewolf let out a low growl, fixing a hungry stare on Severus, who pulled his wand.

Unfortunately, Lupin was too quick. In a second, he had pounced and floored Severus, knocking his wand out of his hand. Lupin raised his head and let out a triumphant howl, before descending upon Severus.

X X X

While this was occurring, Sirius Black had hurried back into the Gryffindor Common Room to meet with James Potter and inform him of his prank on Severus. Entering the common room, he yelled, "Oy! Prongs!" James looked up from the Potions essay he was writing and said, "Yeah?"

"You will not BELIEVE the prank I pulled on Snivellus today!" And he dragged James over to a pair of chairs to tell him about sending Severus to the Shrieking Shack. Lily Evans, another Gryffindor student, initially ignored them, believing that they had pulled another immature prank on Severus, and angered that she had been unable to prevent them from bullying him, but her attention was caught when James yelled, "YOU DID WHAT?", startling her. James immediately got up and ran out of the room. Interested, Lily got up and followed him out. The Fat Lady commented, "One of these days you'll be caught out of curfew, and I will not be covering for you!" James rushed down to the Great Hall and ran out the doorway, Lily close behind. He ran to the Whomping Willow, grabbed a stick, and pressed the knot, causing the tree to freeze. Then Lily saw one of the strangest sights in her entire life.

James had bent down on all fours, and slowly, he began to change. Hair was sprouting all over his body, and hooves slowly began to emerge from his hands and feet. Finally, antlers sprouted from his head.

He's an Animagus? thought Lily. The stag-James proceeded to charge forward into the opening underneath the Willow, followed shortly by Lily. "Lumos", she said, lighting her wand. James and Lily moved through the tunnel, finally reaching a door.

Then they heard a terrible noise. It was Severus, and he was crying out, "No! No! Lupin, please, please don't-" And then they heard a sickening crunch, followed by a terrible scream. The stag pushed open the door, and Lily was greeted with one of the worst sights in her life.

A furry, wolf-like creature was bent over one of her dearest friends, gnawing and clawing at him, as he writhed in pain. "NO!" yelled Lily, causing the creature to look up, emitting a low growl. Lily sent a Blasting Charm at the wolf, sending it tumbling through a window, pursued by the stag. She bent over Severus, who was coughing in pain, blood pooling out around him. "Oh Sev... Sev... Please... please don't be dead..." as she cast healing charms upon him. The wounds slowly began to heal. Eventually, the blood flow stopped, and Lily checked his pulse; it was weak, but it was there, and steady. Looking out the broken window, she could see the stag pinning the wolf down with its antlers. Confident that James could hold it off for now, she muttered, "Mobilicorpus", and guided his body through the passageway, into the castle, and up to the Hospital Wing. She knocked on the door, and Madam Pomfrey answered, "Yes?"

"It's Severus Snape, Madam Pomfrey. He was attacked by a werewolf in the Shrieking Shack."

There was a long pause. Then, "Bring him in." And she opened the door. Glancing at Severus's body, she said, "He was attacked by a werewolf?"

"Yes. At least, I think it was a werewolf." replied Lily. "And in the Shrieking Shack?" "Yes."

All the color in Madam Pomfrey's face drained at Lily's last statement. Then she asked, "H-how is he now?"

"When I found him, he was severely wounded. I cast several healing charms on him to seal the wounds so he wouldn't bleed to death."

"Is he stable now?"

"I checked his pulse. It's weak, but it's steady."

"And, tell me- do you know why he was in the Shrieking Shack?"

"No."

Madam Pomfrey sighed. "He'll have to stay here for about 3 days. Werewolf bites are very, very serious. I'm sorry to tell you this, but I'm afraid that werewolf may have passed it on to him."

"I don't care." said Lily defiantly.

"You don't? Why not?" questioned Madam Pomfrey.

"He's my friend. We've been friends since we were kids- before we went to Hogwarts, even."

Madam Pomfrey smiled. Before going to attend to Severus, she said, "For all the verbal abuse you hurl at James Potter and his friends, you're more like him than you think..."