Harry was the last one to enter the Head's office, after Sirius, McGonagall and the other twelve professors (no one had bothered to call Binns). Professor Fence took his inseparable chest with him.

Although Harry already knew what he would find in the Head's office, he couldn't help gaping when he saw the impressive mirror, cracked from side to side, behind the Headmistress' desk.

The room was crowded, and the members of the Committee looked stunned. No wonder. If Severus had followed their plan, the Aurors had been frozen, and Severus had just undone the Freezing Charm. Nulligan was apparently trying to take the reins of the situation, but the room was full and everyone's eyes were on Severus.

"The explanation for the events that have been observed in this castle is quite simple," said Severus, positioning himself between the tapestry and the mirror. He spoke in barely more than a whisper, but his mere presence was enough to keep the audience silent. Even Nulligan stopped talking, and frowned at Severus. Although Severus wasn't the tallest wizard in the room (Sirius and two of the Aurors were taller than he was), he seemed to loom over all of them. With a wave of his wand, Severus opened all the windows in the office, and a cold, piercing wind entered, bringing with it the scents and sounds of an approaching storm. "In this very room, a crime was committed. An important hallow of our castle was stolen. Like you, I didn't discern the signs at first; I couldn't see what was right before my eyes. But now I can see clearly: someone in this castle is trying to show us who stole the sword of Gryffindor, and where the sword was hidden."

"How can this be?" asked Flitwick.

"Listen to what I have to say and you shall know, as I do, how this crime has been committed," said Severus. "A water lily, a helmet, a plume, a tapestry and, last but not least, a cracked mirror. Why, ladies and gentlemen... There is a celebrated poem which contains all those elements!"

"The Lady of Shalott, by Alfred Tennyson!" exclaimed Minerva, shaking her head. "How could I have missed the clues?"

"Exactly, my dear Headmistress." Severus made a dramatic gesture with his head. "I can see the whole scene as plainly as if it were happening right now," he said, spinning around and pointing his wand at the tapestry. "'Willows whiten, aspens quiver, / Little breezes dusk and shiver / Thro' the wave that runs for ever'," recited Severus, indicating the willow on the tapestry. "'There she weaves by night and day / A magic web with colours gay.'"

"The tapestry!" exclaimed Remus.

"Yes, our criminal was weaving evil schemes. 'And moving thro' a mirror clear / That hangs before her all the year, / Shadows of the world appear'" declaimed Severus, a fanatical gleam in his eyes. "'She left the web, she left the loom, / She made three paces thro' the room'" In three steps, Severus reached the south window, which opened to the lake. Everyone turned to him and followed his movements. "'She saw the water-lily bloom, / She saw the helmet and the plume, / She look'd down to Camelot.'"

Severus turned around to face his audience, pointing his wand at the tapestry again. At that precise moment, Sirius activated the tapestry's animation spell. The silhouette of McGonagall flying down towards the lake on a magic tapestry appeared on the tapestry that was in the Head's office. A murmur of astonishment arose from the audience.

"'Out flew the web and floated wide; / The mirror crack'd from side to side; / 'The curse is come upon me,' cried / The Lady of Shalott'," recited Severus, in a tragic tone. Some people in the audience widened their eyes; others frowned in bemusement. "A water lily, a helmet, a plume, and a mirror. There is no doubt, ladies and gentlemen. 'Out flew the web and floated wide'. Our thief flew on a magic tapestry and landed by the lake. There, the criminal placed the sword of Gryffindor into a boat."

At that moment, when Severus looked ready to say the name of the criminal, a loud bang was heard in the room, and a few feet from where Harry was, people started to scream and push the others back.

"Calm down, everyone!" shouted McGonagall.

Gradually, as if realising there was no reason for panic, people stopped pushing and shouting. Harry approached the centre of the turmoil and saw Trelawney and Fence sprawled upon the floor, with Fence's chest open and many weird objects scattered around: skulls, bottles, candles, a dried aardvark, a dried crocodile head...

"Are you crazy?" asked Fence, standing up and jumping on Trelawney, who had staggered up and was as pale as a ghost. He shook her by the shoulders. "Why did you do that?"

Trelawney's glasses were lopsided so that one eye was magnified more than the other. She looked utterly mad. "You... you l-lied about the ch-chest?" she stuttered.

"You foolish woman! What did you want, to destroy Hogwarts, so that no one could find out about your crime? If you didn't live in a world of fantasy, you would've realised what my chest contained when I showed you my catalogue." Fence turned to the other people in the room. "Listening to Snape's speech, I deduced who stole the sword of Gryffindor. I myself sold that flying tapestry to Sybill Trelawney."

Pressed by the Headmistress and the other teachers - especially Snape, who seemed to know when she tried to lie - Trelawney confessed and described how she had committed the crime. Then she showed everyone the place where she had buried the glass case containing the sword, at the foot of an aspen tree across the lake.

Nulligan tried to take control of the whole operation, but was systematically and completely ignored. Frustrated, he decided to take measures to leave Hogwarts as soon as possible: he activated the Floo Network and asked the Ministry to send a squad of Hit Wizards.

When Trelawney and Fence were taken to Azkaban by the Hit Wizards, Nulligan called Tadg Fortescue to his office at Hogwarts.

"So, what happened here?" asked Nulligan. "I didn't understand half of it. If you don't make me a report of all that happened, I won't be able to talk to my superiors."

"No problem, Chief, I'll tell you everything. Damn, Chief, you know what? I thought of that Tennyson poem as soon as the plume appeared in the Head's office. A water lily, a helmet, a plume..."

"Then why didn't you tell me?"

"Because it was too obvious!" said Tadg, sighing.

"Haven't you read in the Aurors' Manual that the most obvious explanation is the correct one?" asked Nulligan, feeling hypocritical, since nothing that had happened in that case had seemed obvious to him. "Oh, forget it. Tell me the whole story, from the beginning."

"Right," said Tadg. "The sword of Gryffindor was stolen by that seer..."

"That part I understood," snapped Nulligan, annoyed.

"Fence smuggled magic objects in his free time. It was him who sold the flying tapestry to Trelawney a few days ago."

"The Lady of Shalott tapestry?" asked Nulligan, interrupting Fortescue.

"Yes. Trelawney said she was afraid of being fired by the Headmistress, who had never concealed her disdain for Trelawney's prophecies. So the seer felt the need to show she was worthy. She had already been fired about two years ago, by Dolores Umbridge, and she didn't want to go through the same humiliation again. When Fence showed her the tapestry in his catalogue, the plan began to take form in her mind. She bought the tapestry and continued plotting her plan. On the night of the crime, she felt that the stars were especially favourable. At Slughorn's party, she smelled cabbage and realised the smell came from a cauldron full of Polyjuice Potion. She poured some of the potion into an empty wine bottle and hid it under her shawl. She wears loose, layered clothes, and rumours are she usually hides sherry bottles beneath them."

"A crazy drunkard," grumbled Nulligan.

"Then she stumbled on the Headmistress and plucked one of the Headmistress' hairs out," continued Fortescue, his attention focused on his report. "At night, Trelawney drank the potion, entered the Head's office and stole the sword. She didn't bother to take it from the case, because she wasn't really interested in the sword and didn't want to waste time trying to undo the locking spell that had been cast on it. She took the sword to her chambers and used the tapestry to fly down from the Divination Tower to the lake shore. She stepped into the magic boat, crossed the lake and buried the glass case containing the sword amidst the trees. After that, she returned in the same boat and used the tapestry to try to fly back to her Tower. However, she lost control and flew too high. She ended up in the Astronomy Tower. She managed to enter the Tower; then she went down all the staircases and climbed to her own Tower."

"You forgot to mention that Professor Wyrd saw Trelawney," observed Nulligan.

"Oh, yes, it's true. When Trelawney was still in the Astronomy Tower, Professor Wyrd, who happened to be around, saw her. The effect of the potion Polyjuice Potion hadn't worn off yet, so it was McGonagall's body that Wyrd saw. The next day, after thinking about what had happened, Wyrd concluded the person she had seen was Professor Sinistra, since she was in the Astronomy Tower."

"To sum up: Trelawney stole the sword to fulfil her own prophecy, for fear of being fired," said Nulligan. "The sword didn't matter to her; she just had to hide it. When she realised Snape was about to denounce her, she cast an Unlocking Spell on Fence's chest, and slammed into Fence, to make the chest fall down and open. She tried to turn the table, and ended up spilling the beans."

"Chief, I believe the explanation is more complex. I believe she has a serious problem with alcohol, and is becoming paranoid. Being the son of an alcoholic, I recognise the symptoms," said Tadg. "She thought the Headmistress didn't think much of her, and..."

"Well, she wasn't wrong, was she? From what I heard, the Headmistress considers her a fraud. Trelawney didn't need to be paranoid to think she could be fired if she didn't show she was competent."

"Right, even normal people have this kind of suspicion and fear, but..."

"... they usually don't steal a sword to prove their own prophecies are right, and don't try to destroy everything around them so as not to be caught," finished Nulligan.

"Exactly. But it's not just that. I think she really suffers from a Lady of Shalott complex."

"What kind of complex is that, Tadg?"

"Oh, the Victorian woman, who lives in seclusion inside her tower, in a world of dreams," said Tadg. "I think she believed it was her Fate to fulfil the prophecy, you understand?"

"Ah! By Merlin. She has, indeed, fulfilled the prophecy," said Nulligan.

"Yes. We can accuse her of being a thief, but we can't accuse her of being a fraud."

"Tadg, cases like this are bad for my health. Let's get out of here, and then you'll tell me what all that business with the water lily, the helmet, the plume and everything was about."

The sun was rising when everything calmed down again and Minerva called Harry, Remus, Severus and Sirius to the Head's office - which was hers again.

Minerva drew up wooden chairs for all of them. "Have a seat, gentlemen. It seems that almost all the mysteries have been solved."

"What remains to be solved?" asked Harry.

"Oh, little details, like who told the Ministry about the theft," answered Minerva.

"Headmistress... " said the portrait of a red-nosed, corpulent wizard, sounding unsure and frightened.

"Mr Fortescue?" said Minerva.

"Tadg Fortescue is my great-grandson. He has a portrait of me in his sitting room, and we use to talk. On the morning after the theft, when you left for a staff meeting, we portraits talked about the theft, and Skocpol gathered courage and told us what he'd seen. Then I visited Tadg and mentioned that the sword of Gryffindor had been stolen and told him what Skocpol had said... I didn't realise what I was doing. Tadg has some strange ideas, so I always forget that he's also a clever young man. He used the information I provided to be nominated to the Investigation Committee, even though he's brand new to the Ministry."

"Ah!" exclaimed Remus. "That explains it."

Minerva glared at Fortescue's portrait. She would never trust him again.

"I'm sorry, Headmistress. I'll be more careful next time," promised Fortescue.

"Deep inside I am relieved. I was afraid it might have been one of my staff, someone who disagreed with my decisions. After all, we can never be too careful. Fence was a smuggler, and Sybill did all she did just because she supposed I was going to fire her..."

"And was she wrong? You weren't going to fire her?" asked Harry.

"I would probably have tried and convinced her to check into St Mungo's. Alcoholism is a serious problem, and unacceptable for a teacher," answered Minerva. "I do believe she wouldn't have done what she did if it weren't for the disease. I will testify on her behalf and suggest to the Wizengamot that her place is in St Mungo's, not in Azkaban."

"I'm not sure I believe in the idea that alcoholism is to blame for what she did," said Sirius. "For starters, she had to be sober to steal the sword the way she did. Frankly, her plan was quite clever, if a bit bizarre."

"I will never forget her expression when she left escorted by the Hit Wizards," said Severus. "She didn't think twice before opening that chest; she was ready to destroy Hogwarts. She is utterly insane."

"Don't you remember those lines in the final part of Tennyson's poem? 'Like some bold seer in a trance, / Seeing all his own mischance - / With a glassy countenance'. We should have suspected. Did you suspect her?" asked Sirius to Minerva.

"No. I must confess that my suspicions inclined towards more loyal and valuable people," replied Minerva. "I was tormented by the most terrible suspicions! I knew that Severus had that ptyx with him, and Harry had his Invisibility Cloak. The inferences were obvious."

"All inferences pointed to Harry and me," said Severus.

"Precisely. I was very afraid. My head and my heart were in a battle!" exclaimed Minerva. "During Severus's speech at this very room, my doubts started to fade, and I realised what you were doing. I didn't know, however, that Remus and Sirius were involved, too. I should have known!"

"I hope you forgive us," said Remus.

"Oh, I have already forgiven you. You were magnificent, all of you. You had Sybill so scared that she gave herself away. I have just one complaint: I would like to have my office back to its previous condition," said Minerva, gesturing to the tapestry, the helmet, the mirror... "I would also like to have the Barnabas the Barmy tapestry restored and back to its original place."

The four wizards exchanged a guilty and concerned look. Minerva could feel their pain: not only Permanent Sticking Charms and Permanent Freezing Charms were awfully difficult to undo, but restoring that ridiculous tapestry would surely be an ungrateful task.

"Minerva, may I make a little suggestion?" asked Albus's portrait, his eyes twinkling. "I believe a nice cup of tea with scones and muffins is in order, before anything else."

Minerva smiled, happy to have everything back to normal. "What a wonderful piece of advice, Albus!"