Author's Note: The ending of the chapter is rewritten, due to a very good suggestion I recieved from a reviewer, kehlencrow. She asked why I didn't let them be caught, since the Heads of the Houses would have kittens over ten students from three different houses being out of bed at the same time. It struck me as a good idea, and I decided to do a rewrite. And this way, it won't be too much like the first book. Thank you, kehlencrow, for your idea.

Ariel went up to the dorm room after spending two hours in the library to discover that her bed hangings were green, the pillow and quilts lying in a jumble next to her bed, and her trunk was upturned. She swiftly transformed the hangings red again and remade her bed. She was in the process of righting her trunk when Daphne came in. "Ariel, you have to warn Nick and Harry. Malfoy's not going to show up for the duel. I heard him talking about it during dinner. He bragged how he had set Harry and Nick up and he said he was going to tip Filch off after dinner."

Ariel made a face. "Why am I not surprised? Typical Malfoy. I knew Harry and Nick shouldn't have agreed to the duel in the first place, but they wouldn't listen to me." She thought for a moment and opened her mouth again when Tracey Davis walked in.

"Ariel, Draco's setting -," Tracey broke off when she realized that Daphne was in the room and turned bright red.

"What were you going to say, Tracey?" asked Ariel sweetly. "That Malfoy's setting Harry and Nick up? Daphne already told me."

Tracey looked at Daphne in surprise. "You have? But I thought you hated Ariel and everything."

"Well, I thought you hated Ariel," returned Daphne. "So I'm surprised that you came in to tell her about Malfoy's plot."

"Well, I didn't like her very much at first," admitted Tracey. "But what she said about Slytherin's repuation did have a point. I've been thinking things over the past few days and realized Ariel's right. Besides, Draco's annoying, and Pansy gets on my nerves. Since I had a chance to make Draco's plot backfire, I took it."

"I see," said Ariel, raising a brow. "So what-"

"I can't stay and talk," interrupted Tracey. "I just came in to warn you under the pretense of getting a book. Pansy's waiting." She grabbed a book and headed for the door, turning once to say, "Sorry about upturning your trunk and bed coverings. I didn't take part, but Pansy and Millicent did. And I won't mention about Daphne being friendly with you, Ariel."

When Tracey was gone, Daphne and Ariel exchanged looks. "Do you think we can trust her?" asked Ariel.

"Partly," replied Daphne. "I think Tracey was telling the truth, but I wouldn't go as far as being her friend. Though she is nicer than Pansy and Millicent. I certainly wouldn't tell her about the Occlumency lessons or anything else that's important, however."

"Okay, how am I going to warn Harry and Nick?" asked Ariel. "Well, I can warn Harry, since he told me the password to the Gryffindor common room, but I can't go to the Hufflepuff common room since Nick never told me the password."

"You can go to the Gryffindor common room and warn Harry," replied Daphne. "I'll go to the Hufflepuff common room and ask one of the Hufflepuffs to pass on the message to Nick."

Pansy, Tracey, and Millicent swept in the room. "Why didn't you join us, Daphne?" asked Pansy.

Daphne started and answered, "Er, I was feeling tired and came up to rest, Pansy."

"Really?" inquired Pansy. "Then why are you sitting on the edge of your bed rather than lying down?"

"I was lying down!" exclaimed Daphne. "I just happened to sit up when you entered because I was about to go to, er, the loo." She stood up and went to the bathroom. A minute later, Ariel went to the bathroom as well. It was empty, enabling them to have a quick conversation.

"Now what?" demanded Ariel. "It's almost nine o'clock and all the students are supposed to be in their respective common rooms. It's going to be rather difficult for us to sneak out."

"We'll just wait for Pansy, Tracey, and Millie to go to bed," responded Daphne. "Once they're asleep, we'll sneak out and warn Harry and Nick. The time for the duel isn't until midnight, so we have some time. We'll just make sure not to get caught."

Ariel considered for a moment, then decided to tell Daphne about the Invisibility Cloak Aunt Lia had given into her keeping. The two girls decided it would be best to sneak out under the Cloak to warn Harry and Nick, then returned to the dorm room, a minute apart from each other.

Ariel and Daphne waited impatiently for Pansy, Tracey, and Millicent to go to bed. They didn't until eleven o'clock, however, and it was fifteen minutes to midnight when Ariel and Daphne were certain they were asleep. The two girls picked up their shoes and Ariel silently unlocked her trunk and took out the Invisibility Cloak. The common room was empty. The two girls quickly put on their shoes, got under the Cloak, and slipped quietly out.

"Harry and Nick will have probably set out for the trophy room now, so we might as well go there too," whispered Daphne. Ariel nodded and they made their way toward the trophy room. Six minutes later, they arrived, bumping into Nick, Justin, Susan, and Hannah.

Ariel pulled off the Cloak and hissed, "What are you guys doing here?"

"Nick told us what he was going to do," answered Susan. "We were trying to stop him and followed him out, and it turned out we couldn't get back in our common room as the lady in the portrait had gone on a nighttime visit to her boyfriend in another picture."

"What are you and Daphne doing here, Ariel?" demanded Nick in a harsh whisper.

"Warning you!" hissed Daphne. "I heard Malfoy brag about how he set you and Harry up during dinner. He tipped the two of you off to Filch!"

"I can't believe that-" began Nick, but he was interrupted by the arrival of Harry, Ron, Hermione, and Neville.

"Why are you all here?" asked Justin.

"Well, I was seeing Harry off," began Ron. "But someone had to interfere!"

Hermione made a face. "I followed Ron and Harry out, trying to stop Harry from going. When he wouldn't listen, I turned to go back in, but the Fat Lady had gone on a nighttime visit. So I ended up joining Harry and Ron."

"I forgot the password," said Neville. "I came back from the Hospital Wing and couldn't get in, so I waited out in the hall. The Bloody Baron passed by two times, so I joined Harry, Ron, and Hermione. What about you guys?"

"We were trying to stop Nick and ended up getting locked out of our common rooms too, so we joined him," replied Hannah.

"And Daphne and I are here to warn Harry and Nick!" snapped Ariel. "Malfoy set this up! He tipped off Filch, who's going to be here in a few minutes! We'd better leave!" Just at that minute, the sound of someone approaching could be heard. The group quickly ran into the trophy room and out the opposite door. Neville was the last one out the door and it shut just as the voice of Filch could be heard.

Harry pointed and they all began creeping down a long gallery full of suits of armor. Unfortunately, Neville tripped and crashed into a suit of armor. "RUN!" shouted Nick, and they all sprinted down the gallery, not looking back to see if Filch was following. They swung around the doorpost and galloped down one corridor then another, Nick in the lead without any idea where they were or where they were going.

They ripped through a tapestry and found themselves in a hidden passageway, hurtled along it and came out near their Charms classroom, which they knew was miles from the trophy room.

"I think we've lost him," Harry panted, leaning against the cold wall and wiping his forehead.

Neville was bent double, wheezing and spluttering. Ariel glared at Nick and Harry. "This is all your fault for accepting the duel and dragging us into it."

"Well, you could have warned us sooner!" retorted Harry.

"I would have except Daphne and I had to wait until our dormmates were asleep before slipping out to warn you!" snapped Ariel.

"Enough," said Susan. "Let's get going back to our common rooms."

It wasn't going to be that simple. They hadn't gone more than a dozen paces when a doorknob rattled and something came shooting out of a classroom in front of them. It was Peeves. He caught sight of them and gave a squeal of delight.

Ariel and Daphne groaned. Harry pleaded, "Shut up, Peeves - please - you'll get us thrown out."

Peeves cackled. "Wandering around at midnight, ickle firsties? Tut, tut, tut. Naughty, naughty, you'll get caughty."

"Not if you don't give us away, Peeves, please."

"Should tell Filch, I should," said Peeves in a saintly voice, but his eyes glittering wickedly. "It's for your own good, you know."

"Get out of the way," snapped Ron, taking a swipe at Peeves - This was a big mistake.

"STUDENTS OUT OF BED!" Peeves bellowed. "STUDENTS OUT OF BED DOWN THE CHARMS CORRIDOR!"
Ducking under Peeves they ran for their lives, right to the end of the corridor, where they slammed into a door - and it was locked.

"This is it!" Ron moaned, as they pushed helplessly at the door. "We're done for! This is the end!"

They could hear footsteps, Filch running as fast as he could towards Peeves's shouts. Ariel pushed Ron aside roughly, tapped the lock, and snapped, "Alohomora!"

The lock clicked and the door swung open - they piled through it, shut it quickly. Neville, Ariel, Harry, Justin, and Nick pressed their ears against it, listening.

"Which way did they go, Peeves?" Filch was saying.

"Quick, tell me."

"Say 'please'."

"Don't mess me about, Peeves, now where did they go?"

"Shan't say nothing if you don't say please," said Peeves in his annoying sing-song voice.

"All right - please."

"NOTHING!" Ha haaa! Told you I wouldn't say nothing if you didn't say please! Ha ha! Haaaaaa!" And they heard the sound of Peeves whooshing away and Filch cursing in rage. They all sighed in relief, but not for long.

Ariel turned around the examine where they were hiding, and just barely managed to keep from screaming.

They weren't in a room, as she had supposed. They were in a corridor. The forbidden corridor on the third floor. And now she knew why it was forbidden. Ariel quickly got the others' attention.

They were looking straight into the eyes of a monstrous dog, a dog which filled the whole space between the ceiling and floor. It had three heads. Three pairs of rolling, mad eyes; three noses, twitching and quivering in their direction; three drooling mouths, saliva hanging in slippery ropes from yellowish fangs.

Nick happened to glance down and saw that the Cerebus was standing on a trapdoor. Ariel noticed this as well, along with Hermione. There was no time to dwell on this, however.

It was standing quite still, all six eyes staring at them, and Nick knew the only reason they weren't already dead was that their sudden appearance had taken it by surprise, but it was quickly getting over that, there was no mistaking what those thunderous growls meant. Ariel groped for the door handle - between Filch and sudden death, she'd take Filch.

The ten of them fell backwards- Ariel slammed the door shut, and they ran right into Filch. He looked positively delighted. "Oh ho ho! Students out of bed! And so many, too!" Ariel quickly bundled up the Invisibilty Cloak and had Nick, who was standing beside her, hide it under his robes. Justin and Hannah looked as if they wanted to run away, but they were too loyal friends to leave the others to face Filch. Neville looked absolutely petrified at having to face Filch just after seeing that huge three-headed dog. Harry patted Neville's hand comfortingly, but he couldn't supress a feeling of doom. They were in big trouble. If Aunt Lia found out about this, she'd probably send a Howler and ground them during the Christmas holidays.

Filch cackled unpleasantly. "I had heard that two syudents might be wandering about the trophy room at midnight, but I didn't expect to catch ten students wandering about near the forbidden corridor. March!"

He forced the ten students down into his office, then asked, "Your Head of House?"

"Professor Snape," said Ariel bravely.

"P-Professor S-Sprout," stammered Susan.

"P-p-professor Mc-McGonagall," gasped Ron, freckles vivid on his pale face.

"Oh ho ho!" cackled Filch eagerly. "Ten students from three different houses! No Ravenclaws are part of this group, are they?" They shook their heads, and Filch looked disappointed at not being able to bring Professor Flitwick into this.

McGonagall, Snape, and Sprout were called in, and they strode into Filch's office with identical looks of fury on their faces. "What is the meaning of this?" demanded McGonagall. "How can ten students from three different houses be out-of-bounds at the same time?"

"I never thought four of my students could behave in such a manner!" exclaimed Sprout, frowning at Nick, Susan, Justin, and Hannah.

"I was expecting that Miss Stenson might do something like this, but not Miss Greengrass," snapped Snape, glaring at Ariel and Daphne.

"I want you explain the meaning of this," snapped Professor McGonagall.

Ariel decided to tell the truth. "Malfoy challenged Harry to a duel in the trophy room at midnight. Harry accepted and Nick volunteered to be his second, while Malfoy chose Crabbe to be his. Hermione and I tried to talk Harry and Nick out of it, but they wouldn't listen. Later, Daphne told me that Malfoy had set Harry and Nick up. He had tipped off Filch and wasn't going to show up at all. Daphne and I were trying to warn Nick and Harry."

"What about the rest?" demanded Professor Sprout. "How could ten students end up being involved?"

"Susan, Justin, and Hannah were trying to talk me out of it," explained Nick. "I wouldn't listen and they followed me out of the protrait-hole to convince me further. I still wouldn't listen and so they turned to go back to the common room, but they couldn't, since the lady in the painting had gone out on a nighttime visit."

"Ron was seeing Harry off," added Hermione. "I followed to try to talk Harry out of it, and ended up being locked out of the Gryffindor common room as the Fat Lady had gone a nighttime stroll. Neville was out in the corridor resting, since he'd forgotten the password, and was too scared to stay out there any longer and joined us. We all met up outside the trophy room and ran when we heard Filch coming."

Snape gave Ariel a swift, piercing look. Instantly she felt a prickle in her mind and quickly did Occlumency, blocking Snape out of her mind. A few seconds later, Harry felt a prickle in his mind and quickly set up his Occlumency shields. He then noticed Snape, glaring at him. The Nick was forced to do Occlumency as well and realized that Snape was trying to probe his mind. He caught a brief glimpse of Snape looking furious before transferring his gaze to Daphne. Luckily, Daphne's head was lowered, so Snape wouldn't be able to probe very well in her mind, as eye contact was needed for Legilimency to work well.

Professor Sprout began speaking, interrupting Snape's attempts at Legilimency. "I am most ashamed at how matters have turned out tonight. Ten students, four of them from my own house, are out-of-bounds! This has never happened before!"

Snape's gaze looked almost murderous as he looked at Ariel and Daphne. "I am very tempted to expel the two of you, Miss Greengrass and Miss Stenson. However, Professor Dumbledore would object to my expelling you over being out of bed at this time of the night, so I won't. However, you will be punished severely."

"You will all be punished severely," snapped McGonagall. "You have all disappointed me. Especially you, Mr. Stenson. I let you off from being punished this afternoon, and this is how you repay me. I won't have you removed, but you are in big trouble."

Sprout thought a moment, then said, "I think fifty points from Hufflepuff and a detention each will do for my students. And I will write to your parents or guardians."

"And fifty points from Gryffindor and detention each as well," said McGonagall. "And I will be writing to your parents or guardians about this incident as well."

Snape hesitated, then said, "I would like to arrange the punishments for my students privately." McGonagall and Sprout nodded and Snape escorted Ariel and Daphne down to his office.

Once in his office, Snape shut the door and turned on the two girls. "You have shamed Slytherin house! I cannot believe you two could do something so foolish! And being caught with a bunch of Gryffindors and Hufflepuffs! Why didn't you just run away? Filch wouldn't have been able to catch the two of you, since he would have been too busy with the others." He glared at them, then said in a cold voice, "I won't take off many points, since I don't want Slytherin to lose the House Cup, but I will take off ten points each. And you both have a week's detention with Filch, starting next Monday! And if I ever find you wandering about the corridors again after hours, I will make it twenty points and a month's detention! Now go to bed!"

Ariel and Daphne scurried off to the Slytherin common room. "Snape was scary," whispered Daphne. "Almost as scary as that three-headed dog. Thank Merlin we weren't expelled."

"I'd almost rather be expelled than have a week's detention with Filch," muttered Ariel. Seeing Daphne's incredulous look, she added, "I said 'almost', Daphne. Oh, and before I forget, I saw that the dog was standing on a trapdoor."

"Then that means it's guarding something!" exclaimed Daphne. "Prehaps it's guarding the thing Hagrid had to get out of Gringotts!" They arrived at the Slytherin common room then and after saying the password, quietly entered. They decided to talk about this later, and silently slipped up to their dormroom and went to bed.

In the Gryffindor common room, Hermione yelled at Harry and Ron for getting them into trouble. "You idiots! Thanks to you, I'm in trouble, and you've cost Gryffindor fifty points! We're lucky not to be expelled. Oh, my parents will be so disappointed that I managed to get in trouble during my second week of school once they read the letter Professor McGonagall sends them! I told you not to go to the duel, but you wouldn't listen, and had to drag poor Neville into it too! We almost get eaten by a huge three-headed dog who's guarding a trapdoor, and then get caught by Filch and in huge trouble with our heads of house! If you and Nick weren't such idiots to go and accept Malfoy's challenge, Ariel, Daphne, and Nick's housemates wouldn't have been involved either!"

"Hermione, I feel terrible about it too," said Harry, finally able to get a word in edgewise. "Aunt Lia is going to freak when she finds out what happens and will probably send me and Nick Howlers, if she doesn't just march into Hogwarts and yell at us in person. I didn't want to get Neville, or anyone else involved with what Nick and I planned to do, but it happened. So just deal with it."

"Oh, and how will the rest of Gryffindor react when they discover that we have fifty points less than yesterday?" inquired Hermione acidly. "I'm going to bed, and I want to have nothing more to do with you, Ron, and Nick."

When Hermione had gone, Ron muttered, "Good riddance. She really gets on my nerves." Then in a louder voice, "We're sorry, Neville, about getting you dragged into all this."

Neville shrugged. "It's a-all right, Ron. Didn't Hermione say that the dog was guarding something?"

Harry nodded. "Yeah, she mentioned a trapdoor. Hermione must have looked down on the floor and saw it. I guess that might be where whatever Hagrid had to fetch from Gringotts is and that three-headed dog is guarding it."

On the way to the Hufflepuff common room, Nick was apoligizing repeatedly for getting Justin, Susan, and Hannah involved and in trouble. Susan sighed. "Well, we didn't have to follow you out of the common room, Nick. It's not that big a deal."

Justin nodded. "And we could have probably escaped when Filch caught us, but we weren't going to abandon you. We're loyal and stick with each other."

"Thanks guys," said Nick. "Well, at least we shocked Snape, McGonagall, and Sprout."

Hannah giggled. "They probably had kittens when they found out that ten students from three different houses were caught out-of-bounds at the same time." Then she turned more serious. "But why is a dangerous dog being kept in Hogwarts?"

"Well, I noticed that it was standing on a trapdoor," said Nick. "I suppose it's guarding something. Maybe whatever it was Hagrid had to fetch for Dumbledore from Gringotts."

Ernie, who was waiting up for them, met them in the common room. They told him what had happened. Ernie was curious about the dog and the trapdoor it was guarding, and was extremely worried when he heard that they'd gotten caught. As it was late, they decided to go the bed and discuss this all later.