Chapter 135: The River of Time

"October thirty-first? Halloween Eve?" Harry stared at the date displayed on the TARDIS. "Why would Neville come back to this time? Does he want to catch Sirius?"

"If that's really his intention, I wouldn't be surprised," Dr. Doudou pulled open the door and peeked out. "But his location seems a bit off."

This was the Forbidden Forest—Harry recognized it instantly the moment he stepped out; it was the place where Neville and Hermione had "just been."

"I suspect Neville's spell is similar to Apparition, requiring intense mental focus," Professor Doudou remarked. "If the time or location in your mind is even slightly off, you end up somewhere wrong."

Harry and the others stayed hidden behind Neville as he hurried toward the castle.

The Neville appearing on the night of October thirty-first came from November twenty-sixth—he didn't know Sirius wasn't a villain, hadn't read the news of his arrest, and still intended to play the hero.

Neville always wanted to be a hero, even when there was no real need.

Just as Harry worried he might run into Sirius face-to-face, a massive creature blocked Neville's path.

It was Buckbeak the Hippogriff—its expression was furious.

"Oh, you big brute, get out of the way," Neville muttered.

But Buckbeak showed no intention of moving aside; instead, it spread its wings and lunged toward Neville.

Neville leapt backward swiftly, dodging the attack. He looked confused—why was this giant horse attacking him?

Buckbeak reared its front hooves and charged again, its sharp beak aimed straight at Neville's chest, as if trying to pierce him through.

"Fine, if you want trouble," Neville growled, drawing his wand. "I'll give you trouble."

Neville's combat skills were far more refined than anything Harry had ever seen—he sidestepped left, twisted his body to evade Buckbeak's charge, then immediately fired a Stunning Spell.

The spell struck Buckbeak's hind leg—but had no effect; instead, it only enraged the creature further. The Hippogriff let out a piercing screech, flapped its wings, and soared low across the ground toward Neville.

"Shi Shang." Neville calmly uttered his most confident spell. Harry saw only a blur of motion before realizing Neville had somehow climbed onto Buckbeak's back, gripping its wing roots tightly.

Buckbeak thrashed wildly, trying to shake the wizard off, but Neville had excellent balance and held on firmly. The wind and scattered feathers blinded Harry's vision, yet in the end, Neville remained firmly seated, repeatedly punching the creature's head.

Perhaps dazed from the blows, Buckbeak turned midair and dove downward, aiming to land on its back and crush its rider.

Just before impact, Neville cast "Shi Shang" again, rolled right in a controlled somersault, and landed steadily on his feet—while Buckbeak, unable to react in time, slammed itself hard onto the ground.

"Thick skin?" Neville raised his wand high. "Try this then!"

A brilliant beam gathered at the tip of his wand, gradually forming a radiant holy sword. Harry watched in astonishment.

This was the spell he himself had learned in last year's Avalon Realm—yet Neville had only heard it described once, and now he cast it perfectly.

"Excalibur of the Oath!"

The blade descended. Buckbeak, still struggling to rise, had no room to dodge—it was struck head-on by a torrent of searing magical energy. Even a creature with such tough hide could barely withstand it.

When the spell ended, Harry saw Buckbeak lay in ruins—large patches of feathers charred and limp, the creature utterly defeated, motionless on the ground.

"Now know who's boss?" Neville sneered.

The fight had been spectacular—but left Harry deeply puzzled. Logically, Hippogriffs were proud, but they didn't attack strangers without cause.

After defeating—and nearly killing—Buckbeak, Neville was exhausted. He crouched on the ground, panting.

"Doctor, look," Harry whispered. "Neville's body is fading."

"Looks like he's returning to November twenty-sixth," Dr. Doudou murmured, stroking his chin. "His spell is extraordinary—it's not just beyond current technology… it's completely outside it. I have no idea how it works."

In Harry's puzzled gaze, he continued: "Normal time travel is irreversible. But Neville's phenomenon is intriguing—he briefly returned to the past, yet upon exhausting his magic, he returned precisely to the moment he left."

"You know how a Time-Turner works: after going back, you must wait for time to pass until it reaches the moment you originally left. But your location and time aren't fixed," Dr. Doudou said. "Because time keeps flowing. But Neville—"

"What do you mean, time is flowing?" Harry asked. "Suppose I go back from two o'clock to one o'clock. When time reaches two o'clock again, hasn't everything remained unchanged?"

"Before the TARDIS was invented, we thought the same," Dr. Doudou said. "You'd assume you could return to the past, and when 'now' came again, nothing would have changed."

"That's because Time-Turners can only send people to the past. But the enhanced TARDIS can travel freely within the past—and that's how we discovered a strange truth."

"Imagine time as a river—or rather, a river just beginning to flow," Dr. Doudou adjusted his phrasing. "It has two parts: the part already passed, filled with water; and the part yet to come, a dry riverbed."

"I understand," Harry said.

"And this river flows forward constantly—each moment, dry riverbed is filled with water. As far as we know, it has no end," Dr. Doudou said. "We who live within time are like fish in the river."

"Now suppose a hand plucks a fish out and places it upstream. That's what a Time-Turner does. Do you understand?"

"So you mean there's an absolute 'now,'" Harry mused. "When we go back to the past, this 'absolute now' still moves forward?"

"Exactly," Dr. Doudou said, pointing to the TARDIS disguised as a forest hut. "The TARDIS can move freely along this river of time—but cannot reach a future that is completely unknown, the dry riverbed."

"But if that's true," Harry frowned, "say I go back from two o'clock to one o'clock, then wait for two o'clock to come again. Doesn't that mean time has already moved to three o'clock?"

"Precisely," Dr. Doudou said. "You could use the TARDIS at two o'clock to go directly to three. And between two and three, there is no Harry Potter anywhere in the world."

"This…" Harry instinctively wanted to ask how the "absolute now" was defined—but suddenly remembered the legend of the Death God, the "taboo" mentioned by Xuan Jun.

If the "absolute now" was defined by His time, then it made perfect sense. Wizards might try to alter what had already happened—but they were forbidden from stepping into realms even the gods had not yet touched.

"And Neville returned to November twenty-sixth," Dr. Doudou said solemnly. "On November twenty-sixth, we saw him return to the past—and immediately reappear in the 'now.'"

"I don't see anything strange," Harry said dismissively. "Maybe the spell just returns him to his starting point?"

"Did you notice Neville's expression?" Dr. Doudou pressed his hand on Harry's shoulder. "He didn't choose to return—it was the spell's natural effect. Meaning, the spell doesn't return him to 'Neville's perceived starting point,' but to the 'true starting point'—the anchor he left in the river of time. Logically, since he lingered here for half an hour, he should reappear half an hour after his departure."

"In other words," Dr. Doudou said, voice low, "when Neville went back in time… time paused."

"I think that's not hard to understand," Harry recalled his Muggle knowledge. "Neville's time-travel spell is Hyper Shi Shang—or Super Shi Shang. It's based on Shi Shang, a spell that accelerates the user."

"Relativity says the closer you move to light speed, the slower time flows," Harry said. "The Neville from November twenty-sixth didn't fully return to the 'now'—there was a brief gap between his disappearance and reappearance. I think because of acceleration, while he spent half an hour in the past, only a few seconds passed in the 'absolute now.'"

"I went to Muggle university too, Harry," Dr. Doudou shook his head. "Relativity refers to the traveler's time. If you think Neville was accelerating, then it's the opposite: the half-hour he spent in the past might have equaled several days in the 'absolute now.'"

"You see—it's the opposite… Oh! Opposite!" Dr. Doudou suddenly understood. "Of course! I get it—he just reversed the polarity."