This is part of an original serialized fiction project written and edited by the author. All story elements and characters are fictional.

“I’ve been tracking his movements,” Gregorio said. “He’s not the first to try to get inside this place — but he’s by far the most persistent. His foundation has resources and connections we never had.”

Lucía leaned slightly toward Teodora and whispered, “What do we do? I don’t know if we can trust him, but he sounds like he knows what he’s talking about.”

Teodora gave a barely noticeable nod. “We’ll question him more. But we need time — time to decide what to do with him, and with the fragment.”

She turned back to Gregorio, raising her voice.

“If you really were a Custodian, you know this isn’t something that can be resolved with words. We need proof of your intentions.”

Gregorio gave a short laugh, though there was no humor in it.

“What kind of proof are you expecting in a situation like this?”

“For now,” Teodora said firmly, “don’t interfere with what we’re doing.”

Before Gregorio could reply, a loud noise echoed from the tunnel behind them — a sharp metallic sound, followed by a faint rumble that shook the walls.

“What was that?” Lucía asked, startled.

Leo lifted his flashlight, pointing it toward the passageway.

“Do you think it’s Méndez?”

Gregorio shook his head, his face noticeably paler.

“No. That’s not Méndez.”

“Then what is it?” Teodora asked, jaw clenched.

Gregorio looked toward the tunnel, his expression darkening. “If someone tried to activate the Echo Chamber — even partially — they might’ve triggered something in the system.”

Lucía frowned. “Triggered what?”

Gregorio pointed at the walls. The carved symbols were beginning to glow softly, reacting to the sound.

“The building’s defense system. If it detects a threat, it will do whatever it takes to neutralize it — regardless of who’s inside.”

Leo stood up straight, eyes scanning the room. “Are you saying this place could attack us?”

“Not exactly,” Gregorio replied grimly. “But it will make the building unstable. If we don’t get out now, we could be buried in here.”

Teodora turned to the siblings. “We have to go. Now!”

Lucía clutched the flashlight tightly but looked back at the pit where they had left the box.

“What about the fragment? Are we just leaving it?”

Gregorio stepped forward. “Leave it. If we try to take it with us, we could trigger more defenses.”

“And what if Méndez finds it later?” Leo shot back, frustration in his voice.

Teodora placed a hand on his shoulder. “If we don’t make it out, no one will be around to stop him anyway.”

Reluctantly, Leo nodded, and the four of them took off toward the tunnel. The walls quivered with increasing intensity, and the glow from the symbols grew brighter, throwing chaotic shadows across the narrow corridor.

“Faster!” Gregorio shouted from behind.

They burst into the basement just as a final tremor rippled through the building. A deafening crash echoed from the tunnel, followed by the partial collapse of its entrance.

“Is it... sealed?” Lucía asked, glancing back.

Teodora exhaled heavily, leaning against the wall for support.

“For now. But we can’t count on it staying sealed forever.”

Gregorio looked at them, his expression a mix of respect and urgency.