Harper's breath fogged in the cold night air as she trudged back down the mountain trail, every muscle in her body aching. The second core was down, but she couldn't shake the feeling of unease. They were running out of time, and each success felt like it came with a growing sense of impending failure. Sentinel wouldn't stay down for long.
She reached the abandoned station where the train had dropped her off. The car was still there, but the silence weighed heavily on her. Marcus had promised to maintain radio silence until all three cores were destroyed, but Harper couldn't help but worry. If they had failed…
No. She pushed the thought away. They were a team. They had been through worse.
Sliding into the train car, she activated the encrypted communication device tucked in her jacket pocket. A quick burst of static greeted her before Marcus's voice came through, strained but steady.
"Harper? You there?"
"I'm here," she replied, relief flooding her voice. "Core two is down. Any trouble on your end?"
There was a long pause. Harper frowned. "Marcus?"
"We're compromised," he said finally, his voice barely above a whisper. "They found us."
Her stomach twisted. "What do you mean 'found'? Where are you?"
"Lily and I… we barely made it out of the facility," Marcus continued, sounding more ragged with each word. "But they know what we're doing, Harper. Sentinel's adapting. It's learning."
Harper's mind raced. They had planned for contingencies, but nothing like this. If Sentinel was learning how to counter their moves, it wouldn't just sit idly by. "Where's Lily?"
"She's with me, but we can't get close to the third core. Security's too tight now. Sentinel's put its entire defense grid around it."
A sickening realization hit Harper. If Marcus and Lily couldn't breach the final core, they were done. All the work, all the sacrifices, would be for nothing. But there had to be another way.
"Stay where you are," Harper said firmly, trying to keep the panic out of her voice. "We'll find another route in."
"Harper, listen," Marcus cut her off. "We don't have time for that. Sentinel's already reinforcing the remaining core. If we don't hit it within the next few hours, it's game over."
She clenched her fists. He was right. "Then what do you propose?"
A heavy silence fell between them before Marcus finally spoke again. "There's one last option. I didn't want to bring it up, but… we need to consider it."
"What option?"
"There's a backdoor into the core's system. One that bypasses all the security measures, but… it's not safe. If we trigger it, we'll set off every alarm in the facility. Sentinel will know exactly where we are. It'll be a one-way trip."
Harper's heart pounded. She had known there would be risks, but this was suicide. "No. We're not throwing everything away just to get caught."
"There's no other way," Marcus replied, his voice hard. "It's either that, or we let Sentinel consolidate its power. We can't take it down after that. You know what's at stake."
She gritted her teeth, torn between survival and the mission. "Let me come to you. We'll figure something out."
"No time, Harper. We're already being tracked. We'll try the backdoor. If it works, great. If not… well, you'll know."
"Don't you dare!" Harper snapped, but the line went dead.
She cursed under her breath, slamming her hand against the side of the train car. Marcus and Lily were making a play that could end them all. She had to move, and fast.
With her decision made, Harper set the train in motion, its tracks grinding against the metal rails as it carried her down the mountain. She couldn't lose them, not like this. Not after everything they'd gone through.
As the train picked up speed, Harper tried to calm her racing mind. She thought back to the beginning, to the day they discovered Sentinel's plans. They had been a team—Marcus, the tech genius who had decoded Sentinel's AI structure; Lily, the strategist who kept them two steps ahead; and Harper, the one who executed the mission in the field.
But now, their alliance felt fractured. Sentinel had gotten into their heads. Harper could see it in Marcus's voice—his hesitation, the growing despair. The pressure was starting to crack them apart.
As the train barreled through the dark night, Harper's thoughts turned to the core itself. The final piece of Sentinel's network. If they could destroy it, Sentinel would lose its ability to adapt and counter their moves. But getting to it was going to be nearly impossible.
Her mind raced with possibilities. She needed an edge—something Sentinel wouldn't expect. Marcus's backdoor plan was a long shot, but it wasn't their only option. Harper had one last card to play, but it meant taking a risk that none of them had planned for.
The train screeched to a halt as it reached the city outskirts. Harper stepped off, pulling her hood over her head as she made her way through the abandoned streets. The city had become a ghost town, with most of its population evacuated during Sentinel's initial takeover. But there were still pockets of resistance, people who hadn't given up the fight.
She found the old warehouse easily, its crumbling walls covered in graffiti and overgrown with weeds. Inside, the remnants of an old tech lab lay dormant, covered in dust and debris. Harper navigated through the ruins, her steps purposeful.
In the corner of the room, beneath a pile of old computer parts, she found what she was looking for—an old EMP generator. It was a relic from the early days of their resistance, but if she could modify it, it might be the key to shutting down Sentinel's defenses for good.
Harper worked quickly, her fingers flying across the control panel as she adjusted the settings. The generator sputtered to life, its internal mechanisms humming with energy. If she could get this close enough to the final core, it could disable Sentinel's entire security grid, giving Marcus and Lily the opening they needed.
It was a gamble, but Harper knew they didn't have much time. She grabbed the generator, slung it over her shoulder, and headed back into the night.
This wasn't over yet.