The next morning, Jeremy was physically present in science class with Mrs. Hertz, but mentally, he was already elsewhere, on high alert. In front of him, his laptop, carefully hidden among his school supplies, was running at full speed, ready to react to any unusual activity from XANA. Every second of silence in the classroom weighed on him, until suddenly, a piercing beep plunged him into urgency: a new tower had just been activated.

The sound, though discreet, echoed in Jeremy's mind like an end-of-the-world alarm. His fingers began to move, quickly sending a message to his friends: "Tower activated. Meet at the factory immediately."

Sitting a few rows away, Ulrich, Odd, and Aelita exchanged a quick, worried look. They all knew what that message meant. Every minute counted now, and the urgency of the situation was palpable.

Yet, as they stood to discreetly leave the class, Ulrich hesitated for a moment. His thoughts lingered on Yumi. The recent events had deeply affected her, and he knew how vulnerable she was. "We'll let her be for now," he murmured to his friends. "She needs to focus on something else."

Jeremy, absorbed by the urgency, nodded in agreement while quickly gathering his things. At the right moment, the four friends quietly left the room, taking advantage of Mrs. Hertz's inattention, and hurriedly made their way to the factory. A palpable tension accompanied them, pressing them to arrive before it was too late.

As they crossed the schoolyard towards the factory, they stayed on their guard, but nothing could have prepared them for what they were about to encounter. Halfway there, several members of Kadic's staff, including Mr. Delmas, the principal, stood in their way. Their familiar faces were now distorted by a cold, mechanical expression. Their eyes, empty and lifeless, glowed with a sinister light, revealing that they were under XANA's control.

Ulrich instinctively clenched his fists, every muscle in his body tensing at the approach of danger. "Jeremy, I think we've got a problem here," he murmured, readying his mind and body for the confrontation that seemed inevitable.

Odd, despite the tension, couldn't help but make a nervous comment: "XANA sent us quite the welcoming committee… And in the flesh! Not exactly the kind I would've invited."

Aelita, usually calm, couldn't hide her worry. She knew this kind of appearance was never a good sign. "We have to get through. Jeremy needs to reach the factory. But William must not be far behind."

As if to confirm her fears, a dark figure appeared behind the staff members: William, arms crossed, a sneer on his lips. "Did you really think XANA would let you through so easily?" he said in a cold voice.

Ulrich felt a surge of anger rising within him, his gaze hardening. "William… You're not going to stop us this time."

William shrugged, as if all of this was just a game to him. "You can always try. But I wouldn't recommend resisting."

Without waiting, Ulrich, Odd, Aelita, and Jeremy prepared to face the XANA-controlled staff. Every second lost brought them closer to the point of no return. Yet, despite their determination, a thought persisted in Ulrich's mind: "Yumi… what would she have done in this situation? Is she safer away from all this, or is she in danger all alone?"

Meanwhile, Yumi, unaware of the events unfolding at Kadic, was participating in a gym class. The running events allowed her to escape, if only momentarily, the darkness haunting her mind. As always, she outperformed her classmates, receiving congratulations from Jim.

"Well done, Yumi! Another crushing victory!" he exclaimed enthusiastically.

Yumi managed a smile, but she couldn't shake the feeling of emptiness overwhelming her. "If only I could run just as far away from my dark thoughts…" she thought bitterly.

At the end of the class, she headed to the locker room, seeking solace in the routine to find some form of serenity. Once ready, she left the locker room, but a familiar presence awaited her in the hallway. Leaning against the wall, his eyes fixed on her with a troubling intensity, William was there.

"Yumi…" he began, his voice soft but tinged with a disturbing insistence. "You seem so alone. Are you trying to run away from something?"

Yumi froze, her heart pounding harder. "William… What are you doing here?"

William moved away from the wall, his movements slow and calculated, while his gaze seemed to pierce through Yumi, reading her most intimate thoughts. "I came for you, Yumi. XANA sent me… He has plans for you. He desires you more than anything in the world."

Yumi took a slight step back, on the defensive. "I have nothing to do with XANA."

William continued to advance, reducing the distance between them, his tone becoming softer, almost reassuring. "You're wrong, Yumi. XANA wants you because he sees something extraordinary, something unique in you. He'll protect you better than anyone. With him, you'll never have to fight alone again."

William's words echoed in Yumi's mind, stirring a wave of doubt she hadn't anticipated. "He's trying to manipulate me, I know that very well… But… Why am I unable to push him away?" she thought, struggling against the attraction she felt.

Sensing the hesitation in her eyes, William continued to press where it hurt. "Why fight against what's inevitable? Join us, Yumi. XANA will give you what you truly desire. You no longer need to fight against him… or against yourself."

Yumi's determination began to waver. A part of her wanted to give in to this temptation, to this promise of relief. William moved even closer, his presence becoming increasingly overwhelming, hypnotic.

"You've always been alone in this struggle, Yumi. But that can change. Let me show you what XANA can offer you. Join us, and you'll no longer have to bear this burden."

William's words seemed to penetrate deep into Yumi's mind, eroding her last defenses. "Maybe… maybe he's right… Maybe it would be easier to give up this fight… To stop suffering… No, I mustn't let him influence me!" she thought, desperately.

Seeing that she was about to give in, William moved even closer, until he could whisper in her ear. "Please, Yumi… Join me. Join XANA."

Then, with calculated gentleness, he pressed his lips to hers, a kiss that sealed his hold on her. In that moment, Yumi's internal struggle seemed to dissolve, as if carried away by the darkness engulfing her.

Her eyes lost their sparkle, her body relaxed, and she collapsed, unconscious, into William's arms, who looked at her with cold satisfaction.

William, now victorious, lifted Yumi in his arms with disconcerting ease. His face displayed a disturbing calm as he softly murmured to Yumi: "Don't worry, Yumi. You're finally where you belong."

Crossing the school with confidence while avoiding the entrance where the others were, William carried Yumi's inert body in his arms, heading towards the factory undisturbed. The students around them continued their activities, the Lyoko Warriors were dealing with XANA's minions, all unaware of the drama unfolding before them. XANA's influence was spreading, allowing him to act without any hindrance.

Upon arriving at the factory, William gently placed Yumi in one of the scanners, a satisfied smile on his lips. There was no turning back. He activated the machine's controls, and within seconds, she was virtualized on Lyoko.

But William wasn't done yet. He entered a nearby scanner and virtualized himself as well, determined to finish what he had started. Once on Lyoko, he materialized near Yumi, who floated in a semi-conscious state, her feet barely touching the virtual ground.

"Come, Yumi," he murmured in a voice both gentle and commanding. "It's time to meet your true destiny."

Without resistance, Yumi followed William through the Desert Sector. The oppressive silence of the place was broken only by their footsteps, echoing on the desolate ground of Lyoko. Suddenly, the Scyphozoa appeared, floating above the ground, its tentacles unfurling, ready to claim its new prey. William turned to Yumi, a last flicker of humanity crossing his gaze.

"It will be over soon."

The Scyphozoa's tentacles wrapped around Yumi, penetrating her mind to implant XANA's will. A slight smile appeared on William's lips as the darkness completely took over Yumi. She now belonged to XANA. And to no one else.

William, satisfied, watched the transformation. "Welcome to our side, Yumi."

At the school, meanwhile, Ulrich, Odd, Aelita, and Jeremy continued to fight against the XANA-possessed staff. William's plan had worked perfectly: he had stalled them, and Jeremy still hadn't been able to reach the factory. The situation was becoming increasingly critical.

"They're not going to leave us alone!" Odd shouted, narrowly dodging a powerful blow from the gardener.

Ulrich, though focused on the fight, couldn't help but think of Yumi. "Did we do the right thing by not calling her? Something doesn't feel right…" he thought, a deep worry gnawing at him.

Aelita, while dodging the attacks with agility, cast a worried glance at Ulrich. "William… he's gone! I have a bad feeling… we have to get through!"

Jeremy, despite the tense situation, suddenly realized that he hadn't checked his computer since they left the classroom. Stricken with sudden panic, he pulled it out of his bag, opened it, and noticed an emergency window popping up on the screen. What he saw froze him with fear.

"No no no… Yumi is on Lyoko!"

"What?!" Ulrich, Odd, and Aelita exclaimed in unison, their faces crumbling under the weight of the news.

"William must have taken advantage of the situation to capture her while we were stuck here! It was a diversion!" Jeremy continued, the panic evident in his voice.

Ulrich felt a wave of terror wash over him. "We have to go help her!"

Jeremy frantically typed on his keyboard, trying to get more information. But the truth that appeared on the screen hit harder than he could have imagined. "Yumi is on Lyoko, yes… but the Scyphozoa… has already captured her. I think… I think she's under XANA's control…"

A heavy silence fell over the group, the horror of the situation sinking in. They had failed to protect their friend, and now, Yumi had become their enemy. "This can't be… tell me I'm going to wake up… this is a nightmare…" Ulrich cried out, stumbling on the spot.

"What do we do now? Do we just charge in?" Odd asked, his voice devoid of its usual lightness.

Ulrich clenched his fists, determined despite the fear gnawing at him. "We don't have a choice… We have to go free her. I refuse to leave her in XANA's clutches!"

The gravity of the situation weighed heavily on them as they hastened towards the factory, dodging each attack from the XANA-possessed staff, knowing that the real battle was just beginning. This time, they would have to face one of their own, and the price of victory would be higher than ever.

Arriving at the factory, the group rushed to Jeremy's lab. The oppressive silence of the place seemed to reflect the despair weighing on them. Jeremy immediately got to work, analyzing the data, searching for a way to save Yumi.

"She's in the Desert Sector," he announced after a few seconds of heavy silence. "But her signal… it's strange. Is it really Yumi?…"

Ulrich stood behind Jeremy, his gaze fixed on the screens. "We're going to bring her back. No matter what it takes."

Odd, usually so carefree, wore a serious expression. "She'll never forgive us if we don't try."

Jeremy nodded, his face tense. "I'll prepare the scanners to virtualize you. But be ready… To her eyes now, you're enemies."

Aelita placed a hand on Ulrich's shoulder. "We're with you, Ulrich. We won't let her down."

Ulrich, determined, nodded. "Let's go get her."

As Jeremy launched the virtualization process, the group mentally prepared themselves for what awaited them. They knew this battle would be the hardest of all. Saving Yumi was no longer just a mission… it was a matter of life and death.

In the scanner, Ulrich closed his eyes, one last thought for Yumi crossing his mind. "Hang on, Yumi. We're coming."