After dealing with Peeves, they followed the ragged-looking Defense Against the Dark Arts professor down another corridor...
A few minutes later, Lupin pushed open the door to a classroom.
It was the same room where, last term, Professor Albus Dumbledore had led them in confronting a Boggart.
"Come in," Lupin said, holding the door with one hand and gesturing with the other. "Find a seat and stay put."
About twenty students filed in and sat down.
The room was dim, the curtains drawn tight, with only a few lamps for light. Apart from the desks and chairs, the rest of the space was taken up by a large cage. Faint traces of blood could be seen inside, and a few large stones were scattered near the front.
Jon noticed a thick sheet of parchment on the desk, but his attention shifted when he thought he heard something—soft, muffled sobbing.
"Look over there," Zacharias whispered.
Following his gaze, Jon spotted a small figure in the back of the cage.
It looked like a little girl, curled up with her back to them, dressed in scarlet-red clothes and wearing a hat.
"Woo... woo..." The child's head was bowed, shoulders shaking in quiet sobs.
The students murmured to each other in confusion—why would a girl who looked no older than four or five be in a Defense Against the Dark Arts classroom?
"Professor Lupin... why is she locked up?" asked Sean Avery of Slytherin, his tone edged with disapproval.
"That," Lupin replied with a smile, "is exactly what today's lesson is about. Perhaps, to you, she looks like nothing more than an innocent child."
Most of the students nodded.
"But that's not the case at all..."
"Could it be a vampire?" Jon heard Steven Lucas whisper beside him.
"Impossible," Madeline Yaxley muttered back. "You don't just catch a vampire that easily."
Jon frowned, recalling something he'd read in Dark Forces: A Guide to Self-Defense. The description matched—a creature that looked harmless, but was anything but.
...
"Watch closely," Lupin said, raising his wand.
One of the stones inside the cage began to shift and change shape, eventually becoming a gray wolf.
It was an impressive feat of Transfiguration.
As the "wolf" padded toward the sobbing girl, several of the girls in the class instinctively covered their mouths, even knowing it wasn't real.
The wolf had nearly reached her when the girl turned around—and the classroom gasped.
Gone was the fragile, timid child. In her place was a squat, twisted creature with a grotesque mouth smeared with blood, taking up half its face, gripping a heavy wooden club.
With a vicious snarl, the dwarf swung at the wolf. There was a loud crack, and the wolf exploded into chunks of stone.
The pity and sympathy that had filled the students' eyes moments ago were replaced by horror.
"Can anyone tell me what that is?" Lupin asked, scanning the room.
Jon raised his hand.
"Very good, Mr. Hart."
"It's a Red Cap, Professor," Jon answered steadily.
"Correct. Five points to Hufflepuff," Lupin said with a nod, motioning for Jon to sit.
"Red Caps," Lupin began, his tone calm but weighted with seriousness, "are classified by Mr. Newt Scamander in Fantastic Beasts and Where to Find Them as XXXXX creatures—extremely dangerous. They often carry heavy wooden clubs and are strong enough to crush a man or animal's skull in a single blow."
"They resemble goblins, but they're harder to deal with and far more cruel. Wherever blood is spilled, you can be certain they are close. They survive by licking the blood of animals—or humans." He paused before continuing. "Despite their strength, they're slow, which makes catching prey difficult."
"However, Red Caps have their own hunting method. They prefer dusk or nighttime, lurking in dark places near large trees or rivers. They turn their backs to the open, cover themselves with their red fur, and disguise their entire body. Then they make a sound like a woman sobbing—so from a distance, they look exactly like a crying child."
"Lone Muggles—especially hunters—are easy prey at such times. They also attack certain wild animals with poor senses of smell, as well as wizards without proper survival skills."
"Fifty years ago, there were over a dozen Red Cap attacks in Britain each year. But in recent decades, Auror hunts have made them rare here. In Northern and Central Europe, and even France, though, they're still common. This particular Red Cap is one I caught in Stockholm just a few weeks ago."
The room was silent now. Even the Slytherins who had looked down on Lupin earlier were listening closely.
Inside the cage, the Red Cap had already turned away, once again disguised as the crying little girl.
"There are plenty of spells that work against a Red Cap, provided you do not succumb to the disguise," Lupin continued, wand raised toward the cage. "But the simplest and most effective is the Severing Charm. Tearing their red fur is deadly to them, and it ensures they can't use the same trick to harm others again."
"The incantation is... Diffindo!"
With a sharp flick of his wand, the Red Cap's fur ripped apart in chunks, falling to the floor. The gnarled creature shrieked in pain as its true form was exposed again.
"There's parchment on every desk—practice on that," Lupin said with a smile, lowering his wand.