A/N: Thank you to everyone who's reviewed! I don't have the time to reply to every review, but I read them all :D

Dumbledore and the teachers seemed to have come down with a severe case of Plot-Induced Idiocy for most of Chamber of Secrets. Okay, so they didn't know for sure what was in the Chamber, but Slytherin is associated with snakes and students are being petrified, so all they had to do was find out if there was a snake that could petrify people, realise it was a Basilisk, and buy a few roosters. Voila, problem solved with no need for Harry to go down to the Chamber. So I've decided to have the teachers act a bit more sensibly.

A note about Tom: my headcanon is that since he made the diary Horcrux when he was sixteen, and it's unlikely a sixteen-year-old student would be as psychopathic as a sixty-something Dark Lord, diary!Tom wouldn't be quite as cruel as Voldemort became. It's probably not canon, but headcanons usually aren't.

Chapter 21: Enemies of the Heir, Beware

Rummaging in our souls, we often dig up something that ought to have lain there unnoticed. - Leo Tolstoy, Anna Karenina

The teachers stared at the message in silence. The students had long since been packed off to their dormitories, and no doubt they were now exchanging weird and wonderful theories about who wrote the message and what it meant.

'The Chamber of Secrets has been opened. Enemies of the Heir beware.' It would be hard to find two sentences more likely to strike terror into the teachers' hearts. Hagrid and Dumbledore were the only ones who had been at the school during the last incident, but everyone had heard of it.

"What should we do, Albus?" Filius asked at last.

The Headmaster sighed, looking every year of his age. "There is nothing we can do, short of giving Veritaserum to everyone who has set foot in the castle since Christmas. We can only take precautions and hope the culprit is caught before someone dies. I believe having the students carry mirrors for the foreseeable future would prevent deaths."

A few teachers gave him bewildered looks. Their thoughts were written over their faces: How can mirrors stop anyone dying?

There was usually a method in Albus's madness (although half the Wizarding world might say there was madness in his methods), so Severus started trying to figure it out. Albus thought mirrors would stop the students being killed. That meant he thought the monster was vulnerable to mirrors. A Gorgon, perhaps? No, there was no record of Salazar Slytherin having anything to do with Gorgons. They were too human, anyway. The monster must be some sort of snake or something snake-like.

Were any sorts of snakes vulnerable to mirrors? Wait a minute; Albus must be mistaken. Myrtle died in a bathroom, where there were plenty of mirrors. Unless…

Oh. Oh, no. When questioned, Myrtle said she saw yellow eyes as she died. What sort of creature could give someone a literal death glare? A basilisk. What happened if the victim saw its eyes in a reflection? They were petrified but not killed.

Severus had always been inclined to believe Slytherin's reputation had been distorted over time, but at the revelation that the Founder kept a basilisk in a school, he had to wonder if everyone else's opinion was right. A basilisk wasn't even an effective weapon; its eyes would kill anyone unfortunate enough to look at it, not just Muggleborns.

"Who could it be?" Minerva was saying. "It can't be Quirrell and He-Who-Must – oh, all right, Voldemort. They wouldn't dare come back here so soon."

"I am certain it is Voldemort, but how he has reopened the Chamber when he appears to have dropped off the face of the Earth is a mystery."

"Perfesser Dumbledore!"

The teachers winced. Hagrid never seemed to realise that what to him was speaking loudly was to them nearly deafening.

Don't tell me he's figured out what Slytherin's monster is and now wants to keep it as a pet, Severus thought as the half-giant lumbered towards them.

"Some 'un's killed 'em!" the groundskeeper gasped.

An awful vision of Draco and Harry lying dead struck Severus with the force of the Hogwarts Express. He promptly shoved it to the back of his mind. He'd taken them back to the Slytherin common room before coming here, after all.

"Who's been killed?" Minerva demanded, looking terrified.

"Me chickens! Some 'un's come an' cut the poor things' heads off! I was wonderin' why they weren't squawkin' and when I went out they was dead!"

That proved the basilisk theory. Whoever the Heir was, they didn't want to take the risk of their pet being killed.

Only years of hiding his real thoughts and emotions kept Tom in Sally-Anne's body from lashing out at the Hufflepuffs who crowded around him. The whole lot of them, even the sixth and seventh years, were trying to reassure each other that the message on the wall was just a practical joke in spectacularly bad taste. They couldn't see how their actions only revealed their vulnerabilities. It was sickening. It was so sentimental it made his teeth rot. Tom consoled himself with the knowledge that he now could manipulate the entire House as soon as he got a body of his own.

"Are you all right, Sally?" Hannah Abbott asked, sitting down next to him. "You look terrible."

Sally-Anne stirred at the back of his mind, struggling to regain control. She was getting weaker and weaker as his hold over her continued. He didn't expect her to survive till the end of term. It was almost a pity. She drove him insane with her maudlin, everyday worries and her descriptions of how handsome various boys were, but he'd gotten used to her being around. If it was possible he would like to take her with him when he regained his body, but that was impossible. She must die or he would be trapped like this, tied to the diary, until someone else foolish enough to write in it came along.

It was a pity she wasn't a Pureblood, or he would have insisted she give the diary away and she wouldn't have to die.

"I'm fine," he said. Even he couldn't tell if it was a lie.

This would all be over soon. Dumbledore would have to leave Hogwarts at some point when Hagrid was discovered with that dragon egg. He could take Sally-Anne down to the Chamber then.

A hush descended on the Slytherin common room when Professor Snape entered. The only time Draco had ever seen him look so grim was during Pettigrew's questioning.

"Is everyone here?" he asked Flint.

The prefect nodded. "We've checked twice, once before Potter came back and once after."

"Good." The Head of Slytherin turned to the crowd of gathered students. "As no doubt you all know by now, someone has written a message in blood on the second floor wall. The message claims that the Chamber of Secrets has been opened. If you don't know what that is, I advise you find out quickly. If you do know, then you can guess why Professor Dumbledore is taking precautions to ensure your safety."

A few people snorted – very quietly. The sense of dread that hung over the other Houses had affected even the Slytherins.

"From now on, you will go everywhere in groups. No one is allowed to set foot outside the portrait unless they are accompanied by a teacher or at least three students." He paused. "No one knows what sort of monster is in the Chamber, so no one knows what is effective against it specifically, but it would be wise for at least one person in each group to take a mirror with them everywhere they go."

Sally-Anne woke up the next morning with no memory of what happened yesterday and feeling sick to her stomach. This had happened with alarming frequency since coming back to Hogwarts. Horrible scenes flashed across her memory, scenes of cutting a chicken's head off and writing something in its blood. Her gaze fell on the innocuous-looking diary sitting beside her bed. Not for the first time, doubt took root in her mind. For the first time, she acted on that doubt.

These blackouts and strange memory losses had only started after she found the diary. It was just possible there was a connection. She would tell someone about what was happening, and if it had nothing to do with Tom, she could apologise for suspecting him and find out what was really to blame.

She refused to think of the possibility it had everything to do with Tom. He was her friend. He'd never do anything to harm her.

Her thoughts filtered through the mental link they now shared, rousing Tom from his sleep. He listened in horror. If she handed the diary over to any of the teachers, all would be lost. He had to manipulate her without raising her suspicions any more. He had to ensure she wouldn't go to a teacher. At the same time he could ensure he met Harry Potter. He'd wanted to meet this so-called Boy-Who-Lived ever since Sally-Anne mentioned him and his supposed defeat of Lord Voldemort.

Why bother the teachers about it? he whispered, subtly influencing her to do his will while making it seem like it was all her idea. You'd feel so silly if you were wrong. Why not ask another student?

What would a student know about this? she thought, quite sensibly.

Tom increased the amount of influence he had over her. It tired him so soon after possessing her, but he couldn't afford to have a spanner thrown in the works now. Not when he was so close to success. Even now he could feel her growing weaker and him growing stronger (and if that made him feel a strange twinge somewhere around where his chest would be if he had a body, it was obviously because he could feel her weakness through their link).

Why not ask Harry Potter? He defeated You-Know-Who. He's a Slytherin; if anyone can tell a Dark object when they see one, it's a Slytherin.

Sally-Anne wavered on the verge of giving in. Tom continued, knowing that if he pushed just a little bit harder she would do what he wanted.

And imagine writing to your parents and telling them you've talked to the Wizarding world's greatest celebrity.

She gave in.

Slytherin shared History of Magic with Hufflepuff. The Slytherins coped with this by pretending the Hufflepuffs didn't exist. On the rare occasions they acknowledged their existence, they pretended that they were condescending to allow an inferior House the honour of sharing a lesson with them, even one as boring as History of Magic. The Hufflepuffs refused to be daunted and always greeted the Slytherins with sunny smiles and attempted to engage them in conversation on everything from Quidditch to the weather.

Draco had a decent education in History of Magic, courtesy of her parents knowing from painful experience how atrocious Binns was. Being a Malfoy, she had convinced herself she had forgotten more than Binns ever knew – which was entirely possible, if you were talking about the history of Dark Magic, but self-delusion if you meant any other kind. She had a set routine for each lesson. First, she bargained with Daphne Greengrass on the way to class over which of them would take notes this time. If she agreed to humour Daphne (because it was just ridiculous to think of a Malfoy losing at anything, except bets with scar-headed Potters), she spent the lesson bored to death while Daphne dozed or daydreamed. If she won, Daphne spent the lesson bored to death while Draco dozed or daydreamed.

This lesson deviated slightly from the norm from the moment Draco walked in to find a Mud – er, Muggleborn – Hufflepuff sitting next to Harry in her seat. She glared at the presumptuous seat-stealer. The little upstart hadn't even the decency to notice. She was too busy talking to Harry. Draco sank into the seat in front of them, next to a surprised Blaise, and listened with all her might to hear what they were whispering about. Binns droned on in the background, making it hard to hear anything they said. She didn't turn round to watch what they were doing because that would make her eavesdropping blinding obvious.

She distinctly heard Harry say, "I think you should see Madam Pomfrey," and then the conversation seemed to be over.

Draco waited impatiently for the end of class. What in Salazar's name could Harry have been talking to that Hufflepuff about? Why did he think she should see Madam Pomfrey?

Sally-Anne followed Harry's advice and made her way towards the Hospital Wing as soon as Binns finally finished. Tom used just enough control over her to ensure she slipped away from her housemates as they congregated into groups. He waited until she was close to the Chamber entrance before possessing her fully.

"Open," he hissed at the tap, ignoring Myrtle's wails somewhere in the distance.

If the basilisk petrified a few students, everyone would think that Sally-Anne had been petrified in some out-of-the-way corner of the castle when she disappeared. They wouldn't think to start searching for the entrance to the Chamber until he had a chance to get away. He couldn't leave at once, though. He wanted to find out more about Harry Potter. There was something odd about the boy. If he didn't know better, he'd say being around him felt like being around the Diadem Horcrux in the Room of Requirement…

The Diadem Horcrux! He couldn't leave it there; if anyone stumbled upon it the consequences would be disastrous. Two animated Horcruxes and Voldemort himself running around Britain would inevitably end in them fighting over which one was "really" Lord Voldemort. Tom would have to either lock it up where no one could find it or find some way to merge with it.

He opened the main gate to the Chamber, Harry Potter temporarily forgotten.

Theo, Blaise and Harry were on their way to the library, mirrors in hand, when it happened. Harry stopped abruptly in the middle of the hallway.

"Listen!" he said.

The other two Slytherins listened.

"Listen to what?" Blaise asked, annoyed. "I don't hear anything."

"But – that voice – there it is again!" Harry started to run back the way they'd come. "Can't you hear it?"

Theo and Blaise exchanged worried glances. Neither of them could hear anything. Was their friend going mad?

"Harry, there's nothing there," Theo said, running after him. "You must be imagining-"

"But I'm not! It's saying it's hungry and it wants to kill but someone won't let it! Don't you hear it? It's on the other side of the wall!"

That confirmed their worst fears.

"Harry, there's no room on the other side of that wall," Blaise said, as calmly as he could. "It's part of the wall around the teachers' gardens. Let's go back to the dormitory. I think you need rest."

"I'm not mad!" Harry said angrily. "It's gone now, but it was there!"

Theo and Blaise each took one of his arms and frog-marched him down the corridor, completely ignoring his complaints and protestations. The three of them rounded the corner and froze.

Percy Weasley and Penelope Clearwater stood next to the wall in the hall in front of them, looking at a handheld mirror with expressions of shock and horror on their faces. That would have been odd enough on its own, since there was nothing behind them, but there was something even worse about them.

They weren't moving.