Inside the Headmaster's Office, inside the Pensieve.
Dumbledore watched alongside William as his memories unfolded, now reaching the critical part of the sequence.
They saw Tywin striding toward the entrance to the Ravenclaw common room, his robes billowing around him.
"Professor Tywin, what are you doing here?"
Robert's words had barely left his mouth before Tywin's pale right hand clutched his ebony wand.
"Stupefy!" Robert was taken completely off guard and dropped to the ground without a chance to defend himself.
Tywin then retrieved a vial of blood and a battered piece of parchment from his robes.
Dumbledore's eyes narrowed as he observed, and he said in a grave tone, "The Three Books of Occult Philosophy, authored by the sixteenth-century wizard Heinrich Agrippa.
"The work describes the relationships between the human body, the zodiac signs, and the planets, and it also contains spells for breaking seals.
"I had always wondered how Tywin managed to bypass Ravenclaw's magic to seize the ring—now it makes sense."
Dumbledore seemed to be explaining this for William's benefit, and William listened intently.
More than that, he was practically salivating. The school library had plenty of restricted books, but they all belonged to Hogwarts, not to him.
After all, who would ever complain about having too many treasures? Those parchments were undoubtedly valuable.
Professor Tywin flipped open the book to a particular page, dipped a raven's feather into the vial of blood, and began to sketch something carefully.
The blood didn't drip but instead formed a complex, shifting symbol in mid-air.
He quickly completed his work, then reached into his collar and pulled out two Time-Turners.
Professor Tywin positioned the Time-Turners at the center of the symbol, and the objects began to float.
He pointed his wand at Robert's head.
"Avada Kedavra!"
Robert's face contorted in agony, his expression twisted with pain. A gust of wind stirred, and the droplets of blood in the air began to tremble.
It was unmistakably a ritual involving blood sacrifice, with Robert as the offering.
As Robert's life slipped away, the short hand of the Time-Turners began to spin wildly.
White smoke emanated from the Time-Turners, guided by Tywin's ebony wand, until it settled on the door knocker.
The knocker absorbed the Time-Turners' energy in one greedy gulp.
The knocker let out a pleased hum, as though it hadn't tasted anything so satisfying in ages, its hunger driving it to crave even more.
But Tywin showed no concern; he'd already stolen three Time-Turners, and now only one remained. He couldn't afford to lose it too.
He excitedly pocketed the knocker, taking it in hand, and then removed Robert's left eye, placing it on the wooden door before departing.
All of this was a message for Dumbledore.
"Thank you, William," Dumbledore said softly. "Let's return."
William's consciousness drifted out of the Pensieve, and he found himself back in the headmaster's office.
Dumbledore was seated at his desk, and William took the chair across, awaiting Dumbledore's response.
"A very complete memory," Dumbledore finally said, "one that confirms my theories. It proves that I was right.
"Since you came to see me, it means you're ready to leave the time loop, so I take it you understand?"
William nodded. The whole affair was extraordinarily complex, and unraveling it required a wizard with a strong sense of logic.
"Professor, the key to this lies with the Time-Turner," William said, choosing his words carefully.
The Time-Turner was a device for time travel, resembling an hourglass on a golden chain. Each turn of the hourglass represented a one-hour journey back in time.
What made the Time-Turner functional was the "Hour-Reversal Charm."
Wizards had encapsulated this spell within a magically treated hourglass, which could be worn around the neck and rotated to move backward by the desired number of hours.
William had first heard about the "Hour-Reversal Charm" in Professor Binns' class when Cho had asked about the Ravenclaw ring.
At the time, William hadn't thought much of it, not realizing the charm's significance until much later, when, after extensive study, he found it in a seventh-year Charms textbook.
Dumbledore's advice to focus on his studies had been deliberate—he had known William would eventually discover the charm.
From that day on, William had suspected that Tywin was using a Time-Turner, which explained how he could be in multiple places at once.
Dumbledore had even hinted that Tywin was behind the Ministry attack.
Why would Tywin attack the Ministry? Because the Ministry held all of the Time-Turners.
This was also why Fudge hadn't publicized the theft. Losing Time-Turners posed the risk of history being altered, and news of this would surely panic the public.
"Now that you understand the Time-Turner, you must also understand how Tywin managed to orchestrate all of this, don't you?"
Dumbledore leaned back in his chair, looking completely relaxed.
"I have a pretty good idea," William replied confidently.
The portraits of former headmasters in the room stopped pretending to sleep; instead, they perked up, eager to eavesdrop openly.
William was calm as he continued. "Since there were four Tywins, it means he must have used the Time-Turner at least three times within the same timeframe."
"The first time was when you went to Ravenclaw Tower."
"I suspect that in the original timeline, you did reach Ravenclaw Tower and encountered Professor Tywin.
"Realizing he couldn't defeat you, he used the Time-Turner for the first time, traveling back to wait at the staircase, where he intercepted you and misled you back to the headmaster's office with information about Voldemort."
Dumbledore nodded. "Indeed. At the time, I had just received a warning from the Grey Lady.
"Had Tywin not insisted, I would have gone directly to Ravenclaw Tower."
William suddenly recalled something from his Sorting day.
That day, Hufflepuff's ghost, the Fat Friar, had mentioned that the Bloody Baron had gone to speak with the Grey Lady, saying something had happened at Ravenclaw Tower.
In retrospect, it must have been Tywin sneaking in.
Either he had gone to steal the knocker or to confirm whether the Ravenclaw ring was indeed the knocker.
The Grey Lady wasn't so simple, either. It was the first time William had heard of a ghost capable of forewarning others.
He felt a surge of curiosity about the Grey Lady.
But William quickly refocused and continued, "When Tywin encountered Snape in the fifth-floor corridor, it wasn't Snape at all; it was Tywin using Polyjuice Potion.
"So, this must have been another instance of the Time-Turner, but not his second use of it."
"Why do you say that?" Dumbledore asked, a hint of admiration in his eyes.
"The Tywin posing as Snape was badly injured, which suggests there had already been several battles between them."
William went on, "In the corridor leading to Ravenclaw Tower, Tywin was ambushed.
"The ambush was planned, and both of them suffered injuries. Afterward, Tywin used the Time-Turner and vanished.
"I believe that was his second use of the Time-Turner."
William took out his wand and deftly stirred the Pensieve, bringing forth the memory of the two Tywins battling.
"Look, Professor," William pointed at a particular moment.
"Tywin initially has no injuries, but the ambushing 'Tywin' in the corridor of Ravenclaw Tower is already hurt.
"After the ambush, both of them bear identical wounds, correct?"
William's words came faster now, his tone resolute. "This means that after the ambush, Tywin used the Time-Turner and traveled back to lay in wait in the corridor.
"He didn't know who had attacked him, even though the assailant looked identical to him. He assumed someone else must have used Polyjuice Potion.
"But as time passed, the attacker never appeared. Instead, the first version of himself showed up!"
William's voice echoed through the office, and the headmasters in the portraits began to murmur among themselves.
William's point was clear: Tywin had encountered his double, they'd fought, and he had then used the Time-Turner to ambush the attacker.
But, in a twist of fate, the Tywin who traveled back was, in fact, his own attacker all along!