By the Pricking of my Thumbs...

Disclaimer: See Chapter 1.

A/N:Thanks as always to my betas, Septentrion and Sempra. Thanks also to everyone who voted for this story in the hg/ss awards. I was very surprised to win.

It all seemed suddenly so very obvious.

Mould, musty clothing... Vaisey and his friends... He should have realised; no self-respecting Slytherin would get caught in the same place twice... Severus glared at the house-elf. 'Now, Eljay.'

Waving his hands, Eljay backed away in horror. 'Elves are f-forbidden from entering the common rooms, s-sir,' he stuttered.

'This is an emergency, elf,' Severus roared. But Eljay stood his ground.

'Very well. I cannot force you...' It was pointless arguing. 'Purdy!'

It took a moment longer than usual, but Purdy appeared, dived behind Eljay with a squeak and peeped around his side nervously.

Despite his increasing agitation, Severus extended his hand towards the trembling elf and spoke evenly. 'I'm no longer angry with you, Purdy, but I urgently need a favour. Apparate me into the Slytherin common room, and we'll put the past behind us.'

Purdy's ears drooped. 'Headmistress Granger...'

'As soon as we're in there,' Severus interrupted, 'I want you to fetch her, too.'

She took a step towards him, but Eljay held her back. 'It is against the rules,' he hissed. 'You may be punished...sacked, even.'

'I will take full responsibility.' Severus offered her his hand once more. 'Please, Purdy.'

With bated breath, Severus watched the battle taking place on the elf's face, but his pleading seemed to have decided the matter. Ignoring Eljay's protestations, Purdy grabbed Severus' hand and Disapparated.

The shocked faces that met their sudden appearance in the dungeons quickly dissolved into expressions of relief. He smirked at a group sitting on one of the leather settees. 'You have my attention, Mr Vaisey.' But his smirk soon faded as his eyes adjusted to the dim light. The Slytherin common room was not somewhere you would ever call cheerful: austere, certainly, but never this bare and depressing. Never.

Severus' jaw tightened as he looked around. Betty's portrait had of course gone, as had the stuffed animals, the Nundu rugs, the dragon-head trophies...all that remained were some ghostly marks on the stonework to indicate they'd every been there. He shuddered, trying to shake the claustrophobic feeling clutching at his heart. The place was about as welcoming as a tomb. With the friendly glow from the skull candle-holders also absent, the scant light from the wall sconces was only serving to emphasise the sepulchral atmosphere.

'What has happened here?' Severus asked through gritted teeth.

He was met with silence.

'Mr Vaisey,' Severus began. 'You have been putting yourself in my way, deliberately wearing filthy clothing, and...' He sniffed. '... not bathing regularly.'

The Slytherins exchanged furtive glances but remained silent.

'Furthermore,' Severus continued, folding his arms, 'I would remind you that your oath does not prevent the discussion of house matters with other Slytherins within these walls.'

They looked at him blankly.

He sighed. 'I am a Slytherin.'

'Oh,' said Vaisey. 'Of course. I didn't think... Well, in that case, sir... After he took Betty away, Professor Burbage said the rugs and ornaments weren't appropriate and... removed them, too.'

Shaking their heads, the others muttered amongst themselves. Severus frowned. Evidently, they were thinking the same thing he was: the Nundu was a protected species, their skins valuable... He began to breathe more easily, hoping that this... desecration, though unforgivable, was all that was amiss.

'And then there's the dampness, sir.'

Severus' heartbeat speeded up again. 'Show me.' He turned towards Purdy, who was staring in abject horror about her. 'I think the Headmistress should see this for herself, Purdy. Don't you?'

'Yes, Headmaster Snape,' the elf said angrily. 'Purdy is thinking the same thing.' She bowed curtly and vanished.

Severus let Vaisey lead the way, following him down the gently sloping corridor towards the dormitories. The smell of damp had hit him as soon as they'd left the common room, and his sense of foreboding was growing with each step. Vaisey paused just before the corridor ended, opening the door on their left as Severus expected, and entered the vestibule around which the boys' dorms were located.

'We try to keep it in check, sir,' Vaisey said, pointing at the walls. 'But it's hopeless.'

Severus touched the stonework and nodded. 'I assume Professor Burbage has been informed of this?'

Under the circumstances, Severus couldn't admonish Vaisey for rolling his eyes like that. It was an inane question, but it had confirmed his suspicions. Burbage had been negligent in his duty; whether this was out of ignorance or malice, he had yet to ascertain.

Vaisey turned away. 'My room's one of the worst,' he said, opening the door to the fifth-year dorm.

Inside, three seventh-years...two of them girls...were busily casting drying charms on the ceiling, walls and beds. They stopped when they saw Severus.

'How long will that last?' Severus asked, looking up.

'Until tomorrow, sir,' Vaisey replied.

'These are the strongest spells we know, Professor,' one of the girls said. 'We don't know what else to do.'

Keep calm. Don't frighten them. 'You've done all you can,' Severus told them. 'But, it's not healthy for you to sleep in these conditions.' He ushered the two girls towards the door. 'Get everyone out of the girls' dormitories. Take what you can carry and head for the common room. The Headmistress should be there by now. Tell her to stay put until I arrive.' He glanced over his shoulder. 'The same goes for the boys. Vaisey, you're with me.'

~HGSS~

Hermione had been enjoying a long soak in the bath when Purdy appeared. Despite the elf's frantic pleading that she should come immediately, Hermione had insisted on dressing first and not budging an inch until Purdy had explained what was going on.

She was therefore partly prepared for the sight that greeted her when they Apparated to the dungeons. The Slytherins stared at her coldly as she took in their living conditions, and for once, Hermione was at a loss for words. She was saved from the embarrassing silence, however, as the first evacuees began trickling into the common room.

The first-years, who had been sound asleep in bed, rubbed their eyes and yawned. Some were clutching books to their chest, others teddies.

'What's going on?' Hermione asked one of the prefects.

'Professor Snape said to stay put until he arrives,' the girl replied.

Further questions were stone-walled. 'Very well,' Hermione said exasperatedly. 'I shall await Professor Snape's explanation. But in the meantime, will one of you please fetch Professor Burbage? He has a right to be here.' She turned to Purdy. 'Some comfy chairs, please, Purdy, and something to drink... and, let's do something about the light, shall we?'

~ HGSS ~

Entering the corridor once more, Vaisey automatically turned right.

'No, this way.'

'But, sir. It's a dead end.'

'Appearances can be deceptive, Mr Vaisey.' Severus paused before the blank wall, hoping that the wards still recognised him. Placing his palm on the stone, he muttered an incantation and pushed. His hand passed effortlessly through the wall. 'Hold my arm,' he told Vaisey. 'I shall only keep you a moment.'

On the other side of the barrier, both wizards cast Lumos and quickly mounted a short flight of steps.

'Where are we, sir?' Vaisey asked nervously.

'Where do you think, boy?'

Meanwhile, Purdy was busy handing out steaming mugs of cocoa.

'When can I go back to bed, miss?' a first-year asked Hermione, sipping hers.

'Soon, I hope,' she replied, kneeling beside her. 'I'm sure Professor Snape won't be...'

'What is the meaning of this?' All eyes turned towards the Head of House as he stormed into the common room. 'Why aren't you all in bed? And I thought I told you, no Transfigured furniture.'

'The latter would be my doing, Professor Burbage,' Hermione said icily, getting to her feet.

'H-headmistress,' Burbage stuttered. 'I wasn't told you were here.'

'Evidently not.'

It was hard to ignore the expressions on the young faces around her: loathing, hope, relief combined with a certain gloating pleasure that Professor Burbage had been Found Out. But, much as she was ready to wipe the floor with him, Hermione was not about to do it in the Slytherin common room...or without being in full possession of the facts.

'I'm waiting for Professor Snape's report,' she said.

'Snape? Oh, he's here, is he?'

Hermione didn't like the sly look that came over his features. 'Yes,' she replied. 'Can you think why?'

Burbage shrugged. 'I have no idea...'

~ HGSS ~

With a broad sweep of his hand, Severus illuminated the domed chamber. Vaisey shielded his eyes against the bright light, becoming aware of a silver lattice pattern which shimmered and stretched like a giant web over the low ceiling and reached down to the floor. On closer inspection, he noticed that parts of it were shining less brightly while in other places the strands were black or missing altogether. Here, cracks could be seen in the rock and water seeping through. He gulped.

'We have caught it just in time,' Severus said. 'It is not as bad as I feared.'

'Is-is that all that's keeping the lake out, sir?' Vaisey whispered.

Severus nodded. 'It is.' He reached into his robe pocket and took out the golden key. 'I shall attempt to make repairs. Take this to the Headmistress and explain what I'm doing. She knows what it's for...and make sure everyone stays in the common room. It's part of the castle and therefore protected by its wards. You will be safe there should I fail. Quickly, now.'

He waited until Vaisey had scuttled back down the steps before surveying the damage once more. Breathing deeply, Severus raised his wand.

It was an ancient spell, almost as old as Hogwarts itself. Created by Salazar Slytherin, it had been passed down to every Head of Slytherin since. Had Burbage not been told that the Net had to be regularly maintained? Had the secret died with Horace Slughorn?

Severus' worst fears were confirmed a moment later. Concentrating on stabilising one of the least affected patches, he was horrified to see the dull grey strands turn black... and spread like a fungus over the ceiling. A large chunk of rock crashed to the floor...

A trap?

The Bastard!

Severus turned and legged it.

He only had a few minutes at best. With water already pouring in, Severus charged through the false wall and yelled at the final few stragglers ambling nonchalantly towards the exit, 'Get out! Run!'

They froze for a split second, stunned by the sight of their Defence teacher sprinting towards them... then registered the water that was following him.

'MOVE!'

Panicked into action, they ran blindly, knocking over a bewildered little first-year, who had just emerged from the bathroom, in their haste. Severus hardly broke stride. Picking her up, he slung the girl over his shoulder and kept on running...

~ HGSS ~

'Professor Snape said to give you this, miss.' Vaisey offered the key to Hermione. 'He's trying to repair the wards, but...'

He was cut off by a loud shriek. 'Oh, my God! Look!'

'What the...?'

Turning in the direction of the sound, Hermione was horrified to see a rush of brackish water flowing towards them. But before anyone had time to think, the torrent hit an invisible barrier and folded back on itself.

'Is anyone else down there besides Professor Snape?' she asked frantically. 'How many are missing?'

'Another four, miss,' one of the Prefects answered. 'Here they come now.'

The water was rising fast as Severus and the others waded the last few feet to safety.

In the confusion and with everyone anxiously watching the entrance, no one noticed Burbage quietly unsheathing his wand while an exhausted Severus finally dragged himself into the common room.

Triumphantly, Burbage struck, casting the curse with lighting speed.

'Rot in hell, you murdering bastard!'

Severus glimpsed the flash, but had no time to defend himself. Instead, he instinctively turned to protect the child in his arms, taking the full blast of the curse. Without uttering a sound, he collapsed to the floor.

'SEVERUS!'