Filch grabbed Maure's robes collar and the children were pushed into Professor McGonagall's Office.

"Professor, students out of bed after curfew."

"Mr. Crawford, haven't Madam Pomfrey told you to go straight back to the dormitory?" asked Professor McGonagall, who was examining the students.

Daniel muttered something in a barely audible volume.

"Speak up, Mr. Crawford, please."

"I can't figure out the answer to the door."

Ariane thought she heard a snigger from Maure.

"What about you four? Why didn't you go back to bed after lesson?"

"We—We—"

"Yes, Miss Claudia?"

Claudia found it hard to think for an appropriate reason to go out late at night.

"I'm clearly disappointed of your behaviour, Professor Snape and Professor Flitwick will be alerted. As to ensure this won't happen again, twenty points will be deducted."

"Twenty?" exclaimed Hugo.

"Yes, Mr. Hugo, each."

Hugo wanted to argue but Claudia pulled him back.

"For your detention, Mr. Filch will take you to Hagrid's hut, and the detention will be taken place at the Forbidden Forest."

"But, Professor," said Maure again. "But I thought Professor Dumbledore had said we weren't advised to have detention in there."

"As to ensure this won't happen again, it is appropriate for you to have detention in the forest. And Mr. Crawford, I will escort you to the entrance."

After watching Daniel got out of sight with Professor McGonagall, the children pursed their lips as Filch escorted them to the grounds.

"Twenty each?" said Hugo. "That's so unfair."

"Use up me and Joanne's fifty each for getting the tests all correct in Herbology, Transfigurations and Charms. Wish I can get more points in Potions, Snape just only give me ten points," said Ariane.

"Ten? I think it's already good enough that he didn't deduct points from our mistakes in the tests," said Claudia.

"Not to mention Dan's test, he nearly failed," added Claudia.

"Everyone would want to curse us for losing eighty points for that. I don't think anyone has lost eighty in a go."

"Let's hope Ravenclaw win that Quidditch."

"Nah, the Gryffindors will beat us down."

"Let's hope we can pass our mid-terms so Flitwick can give us more points."

"Oh, good old days when I can slap students with whips and chains if they talk too much," gritted Filch. "Too bad those corporal punishments are banned."

The children gulped and did not talk until they met Hagrid.

Hagrid was waiting for them at the hut, with Fang, a black boar hound at his heels. He was carrying his large crossbow, and a quiver of arrows hung over his shoulder. Their detention work was to find out the injured unicorns. Ariane was a bit unsure, what if she met the killer and the killer would kill them all too? Thinking that made her shudder much. After practising sending sparks as signals, they headed towards the forest.

"I'll be back at dawn," said Filch, "for what's left of them," he added nastily, and he turned and started back toward the castle, his lamp bobbing away in the darkness.

"We need ter split teams," said Hagrid.

Ariane was just about to be with Claudia and Hugo when Maure interrupted.

"I will go with Anne and Fang," said Maure, who was thinking that a boar hound with big long razor teeth could make a strong team.

"Okay, just wanna let yer know, he's a coward," said Hagrid.

Fang whined, and hid behind Maure. Maure looked frightened as he was told that Fang could not protect him from danger.

"But there're occamys and trolls, and even werewolves!" exclaimed Maure.

"Yep, I hear that there're even lethifolds in the forests," answered Hagrid.

"Wait till my father knows about this."

They went into the forest and parted by the mist.

"I don't have a good feeling," said Ariane.

"I'll protect you then," replied Maure, who was acting to be brave.

"You don't have to, I get a mysterious shield like the shield charm when bad things happened."

"What if it doesn't work?"

"I know it will work."

A snap at the twigs frightened them, and they looked at a shining rock at the ground not far. As they walked closer, the 'rock' was revealed to be a unicorn, with silvery blood gushing out from its abdomen.

"Yuck," gasped Maure as he stepped onto a pool of silvery liquid. "Unicorn blood."

Their voice seemed to have alerted a dark shadow. It was a hooded figure came crawling across the ground like some stalking beast. The cloaked figure reached the unicorn, lowered its head over the wound in the animal's abdomen, and began to drink its blood.

Maure let out a terrible scream and bolted - so did Fang. The hooded figure raised its head and looked right at Ariane - unicorn blood was dribbling down its front. It got to its feet and came swiftly toward Ariane - she couldn't move for fear.

Then a pain like she'd never felt before pierced her head; it was as though her brain were on fire. Half blinded, she staggered backward. The hooded figure glided towards her and made a menacing growl, trying to embezzle her. She heard hooves behind him, galloping, and something jumped clean over Ariane, charging at the figure.

The pain in Ariane's head was so bad he fell to her knees helplessly. It took a minute or two to pass. When she looked up, the figure had gone. A majestic and respectful creature came to her, and she knew it was a centaur. To the waist, a man, with white-blond hair, but below that was a horse's gleaming palomino body with a long, blond tail, was standing over her.

"Are you all right?" said the centaur, pulling Ariane to his feet.

"Yes—thank you—what was that?"

The centaur didn't answer. He had astonishingly blue eyes, like pale sapphires. He looked carefully at Ariane, his eyes lingering on her eyes and her hair.

"You are Rowena Ravenclaw's impeccable descendent," he said. "It is not safe for you to linger here in the forest, especially for you. Mars is shining bright these days, unusually."

Ariane did not know what to say.

"Can you ride? It will quicker and safer."

"My name is Firenze," he added, as he lowered himself on to his front legs so that Ariane could clamber onto his back.

There was suddenly a sound of more galloping from the other side of the clearing. Another centaur came bursting through the trees, their flanks heaving and sweaty.

"Firenze!" The centaur thundered. "What are you doing? You have a human on your back! Have you no shame? Are you a common mule?"

"Do you realize who this is?" said Firenze. "This is the Ravenclaw's daughter. The quicker she leaves this forest, the better."

"Alright, if that's the Ravenclaw's daughter." growled that centaur. "Remember, Firenze, we are sworn not to set ourselves against the heavens. Have we not read what is to come in the movements of the planets?"

Ariane didn't have a clue what was going on.

"Why's he so angry?" he asked. "What was that thing you saved me from, anyway?"

Firenze slowed to a walk, warned Ariane to keep her head bowed in case of low-hanging branches, but did not answer Ariane's question. They made their way through the trees in silence for so long that Ariane thought Firenze didn't want to talk to her anymore. They were passing through a particularly dense patch of trees, however, when Firenze suddenly stopped.

"Ariane Larsen, do you know what unicorn blood is used -for?"

"No," said Ariane, startled by the odd question. "We've only used the horn and tail hair in Potions."

"That is because it is a monstrous thing, to slay a unicorn," said Firenze. "Only one who has nothing to lose, and everything to gain, would commit such a crime. The blood of a unicorn will keep you alive, even if you are an inch from death, but at a terrible price. You have slain something pure and defenceless to save yourself, and you will have but a half-life, a cursed life, from the moment the blood touches your lips."

Ariane stared at the back of Firenze's head, which was dappled silver in the moonlight.

"But who'd be that desperate?" he wondered aloud. "If you're going to be cursed forever, deaths better, isn't it?"

Ariane nodded as if she understood what he was saying.

"You mean that thing is—"

"We centaurs are not supposed to expose the secret of the earth, but I must warn you to be careful."

"Ariane! Ariane, are you all right?"

Claudia was running toward them down the path, Hagrid puffing along behind her.

"I'm fine," said Ariane, barely knowing what he was saying. "The unicorn's dead, Hagrid, it's in that clearing back there."

"This is where I leave you," Firenze murmured as Hagrid hurried off to examine the unicorn. "You are safe now."

Ariane slid off his back.

"Good luck, Ariane Larsen," said Firenze. "The planets have been read wrongly before now, even by centaurs. I hope this is one of those times."

He turned and cantered back into the depths of the forest, leaving Ariane shivering behind him.

Hugo had fallen asleep in the dark common room, waiting for them to return. He shouted something about Quidditch fouls when Ariane roughly shook him awake. In a matter of seconds, though, he was wide-eyed as Ariane began to tell him and Claudia what had happened in the forest.

Ariane couldn't sit down. She paced up and down in front of the fire. She was still shaking.

"Snape must be working Sere—"

"Don't say that name!"

"Okay, You-Know-Who…and he's waiting in the forest... Firenze saved me, but he shouldn't have done so... The centaurs were furious... he was talking about interfering with what the planets say is going to happen... They must show that he's coming back... They think Firenze should have let him kill me... I suppose that's written in the stars as well."

"Hey, remember who's the only wizard You-Know-Who ever afraid of?" asked Claudia.

There was a pause.

"Dumbledore, as long as he's here in Hogwarts, you are safe, and there's nothing You-Know-Who can do around."