"You two go," Chen said, pulling away from them. "I'll cover the rear. If that thing comes after you, I'll slow it down."
"Bullshit," Marcus said flatly. "You're infected. You stay behind alone, you turn, and then we have one more of those things between us and the exit."
"Exactly why I can't go with you." Chen looked at their hand—the black veins were past their wrist now, spreading up their forearm. "If I transform while we're down there, in close quarters, I compromise the mission. This way, if I turn, I'm contained. You finish the job."
Nora's voice shook. "Dr. Chen, there has to be another—"
"There isn't. And you know it." Chen handed her the communications relay pack. "You'll need this to call extraction after. Give me one of the flares. If I feel myself going, I'll burn myself out."
Marcus studied Chen for a long moment, then nodded. He understood. He'd made these calculations before—in Afghanistan, in Syria, in places where someone always has to stay behind. He handed Chen a flare and his tactical knife.
"If you're still you when we come back up, we'll get you out," he said. "If you're not..."
"Shoot me," Chen finished. "Center mass. Don't hesitate."
Nora looked like she wanted to argue, but time was bleeding away. She touched Chen's shoulder—careful not to make skin contact with their infected hand. "Thank you, Dr. Chen. For everything."
They descended into the darkness, their flashlight beams swallowed by the spiral staircase. Chen heard their boots on metal, growing fainter. Then silence.
Chen was alone.
The infection burned up their arm now, reaching their shoulder. They could feel it at the edge of their thoughts—not words exactly, but impressions. Curiosity. The desire to understand. And underneath that, something vast and ancient and utterly alien.
Chen positioned themselves at the top of the stairwell, flare in one hand, knife in the other. If anything came up those stairs after their team, it went through them first.
The corridor behind them was quiet. The crystalline growths on the walls had retreated from the heat, leaving only residue. But Chen could feel them—feel it—watching. Waiting.
"Dr. Chen."
Chen spun. Dr. Tanaka stood in the corridor. Or what looked like Dr. Tanaka. But Chen could see through the illusion now—the too-smooth skin, the dead eyes, the proportions that didn't quite match.
"You stayed behind," it observed. "Interesting choice. Self-sacrifice. Very human."
"Stay back," Chen warned, holding up the flare.
It didn't move closer. Just stood there, studying them. "The infection in your arm—you're fighting it very hard. Most humans don't fight this hard. They accept integration. It's peaceful, Dr. Chen. Like falling asleep."
"I've seen what you do to people. That's not peace. That's consumption."
"Is there a difference?" It tilted its head. "When you eat an animal, you consume its flesh to sustain yourself. Its atoms become your atoms. Are you a murderer? Or are you surviving?"
"Animals don't have consciousness like we do."
"And I don't have consciousness like you do," it countered. "We're different forms of life, Dr. Chen. Neither superior, neither inferior. Just... different. Why must that difference mean one of us has to die?"
Chen's arm was almost entirely black now. The infection had reached their chest. They could feel their heart beating faster, their body fighting the intrusion. Or was it fighting? Some part of them—small, growing—whispered that the entity was right. That understanding would be better than fear.
Chen shook their head violently. "Get out of my head."
"I'm not in your head yet. That's you, Dr. Chen. Your own thoughts. Your own doubts. You've studied emerging infectious diseases. You know that sometimes the virus isn't evil—it's just trying to survive and reproduce. You don't blame the virus. Why blame me?"
Below, Chen heard a distant sound—metal clanging. Marcus and Nora had reached sub-level 2.
The Tanaka-shape took one step forward. "They're going to ignite the incinerator. Burn the station. Burn you too, Dr. Chen. They'll have to. Even if you're still conscious, still yourself, the infection will survive in your tissue. They can't risk it. You know this."
Chen did know this. The mission came first. If Marcus and Nora succeeded, Chen died here. Best case scenario.
"So why not surrender?" it asked gently. "Let me in completely. I'll preserve you. Everything you are, everything you know, everything you love—it'll continue. Enhanced. Part of something greater. Isn't that better than burning alive?"
The flare trembled in Chen's hand. Their infected arm hung limp—they couldn't feel it anymore. Couldn't move the fingers.
"Last chance, Dr. Chen. Join me willingly, or die alone. Choose."
From below, another sound: a heavy metallic thud. The incinerator door opening.
Chen looked at the flare in their hand, then at their blackened arm. The entity stood before them, wearing Tanaka's patient, understanding expression. Offering immortality. Offering an end to loneliness and fear.
Or offering slavery wrapped in pretty words.
Chen thought of Sergei, crossing himself before sacrificing everything. Of the Polaris crew who fought and died trying to contain this thing. Of Marcus and Nora, risking everything to finish what others had started.
Some choices weren't really choices at all.