Nyelle screamed again, and I ran.
The staircase twisted beneath the station, descending through layers of stone that shouldn’t have existed beneath a modern city. Blue light pulsed inside the walls, illuminating symbols that shifted whenever I tried to study them directly. My injured shoulder protested with every step, but I kept moving, following my sister’s voice before it disappeared into the depths.
"Nyelle!"
"Veyric, don’t come down here!"
Her warning only made me run faster. My mother and the man in the white coat shouted behind me, but their voices faded as I descended. I’d spent the entire night trying to reach my sister, and I wasn’t going to let another locked door or hidden chamber keep me from her.
The staircase ended at a narrow landing, where a corridor led to a circular doorway. Metal scraped against stone beyond it, followed by a muffled thud that made me break into a sprint. I pressed my hand against the entrance, and the blue line beneath my skin brightened as the door slowly opened.
The chamber beyond resembled an enormous underground well. A circular platform hung above a dark shaft, supported by thick metal beams, while six empty frames stood around its edge. Their carved symbols resembled the three-circle mark on my mother’s ring, although I couldn’t understand the additional lines.
Nyelle stood on the platform, gripping a railing with one hand and pressing the other against her chest. Silver lines formed a circle beneath her feet, pulsing with each breath, while narrow bands of light followed her movements around her ankles. Opposite her stood another girl with Nyelle’s face, height, and torn jacket, except her clothes were clean and her hair perfectly arranged.
"Veyric, stay back!" my sister shouted.
I stepped onto the platform, and the circle brightened. Pain flared through my right hand as the second Nyelle turned toward me with a familiar smile.
"You came," she said.
I ignored her. "Nyelle, are you hurt?"
"I don’t think so, but every time I move, the floor pulls me back." She glanced at the silver bands around her ankles. "I’ve tried leaving. It won’t let me."
The other girl tilted her head. "She doesn’t understand what the circle is for."
"Then explain it."
"It isn’t a prison."
"Then why can’t she leave?"
"Because the structure hasn’t finished deciding which one of us belongs here."
I moved between them. "There’s only one Nyelle."
"That’s what you believe."
The blue line in my palm pulsed, and pressure gathered behind my eyes. For an instant, the chamber blurred into a memory of two children standing on opposite sides of a glass wall, one crying while the other reached toward a woman holding a baby. The image vanished before I could understand it, leaving me unsteady and Nyelle reaching anxiously for my arm.
"I’m fine," I lied.
The second girl noticed my reaction. "You remember more than you think."
"I’m not interested in riddles."
"You should be. They’re the only things keeping you alive."
The silver circle flashed, sending pain through my palm. A blue line extended from my hand to the platform’s center, joining the markings around Nyelle, and all six frames illuminated at once. The metal supports groaned as something shifted inside the shaft beneath us.
"Veyric, stop!" Nyelle shouted.
"I’m not doing anything!"
"Then tell your hand to stop!"
The blue markings had spread across my wrist, forming a pattern that resembled the three-circle symbol. The System appeared before my eyes.
[ORIGINAL RESPONSE: ACTIVE.]
[SECONDARY SUBJECT: WITHIN RANGE.]
[SEPARATION CONDITION: UNMET.]
"One of us has to leave," the second girl said.
Nyelle shook her head. "You said the structure would let us go when the response was complete."
"It will."
"Then why are the doors closed?"
"Because you keep trying to leave before it finishes."
Nyelle looked at me. "She keeps saying things that almost make sense, but whenever I ask what happens afterward, she changes the subject."
"Sounds familiar," I said.
Despite her fear, Nyelle gave me an incredulous look. "Are you seriously making jokes right now?"
"If I stop, I might start screaming."
"Warn me first."
Her answer was unmistakably Nyelle, and some of the tension left my chest. I reached toward her, but the blue line tightened, forcing me to stop as another pulse burned through my palm.
"You’re making it worse," the second girl warned. "The structure recognizes both of you, but it can’t maintain both responses in their current state. If the connection completes, one of you will no longer be necessary."
Nyelle’s face drained of color. I stepped toward the other girl, but the platform shook, and her appearance flickered. Beneath her familiar face, I saw a pale silhouette outlined in blue, as though someone had drawn a human body around an empty space.
"I didn’t want it to happen like this," she whispered.
"Then why are you doing it?" Nyelle demanded.
"Because I don’t know how to stop."
That answer changed something, though it didn’t make me trust her. Fear wasn’t proof of innocence, but attacking her without understanding the mechanism would be reckless. I crouched beside the circle and examined the lines converging at a dark stone embedded in the platform.
Three circles were carved into its surface.
The third was incomplete.
I remembered my mother’s ring, the old device, and the door that had opened when my hand approached it. The structure was responding because something in my body matched a pattern the facility had been designed to recognize. I reached toward the stone, but both girls shouted at once.
"Don’t touch it!"
Their voices overlapped so perfectly that I couldn’t distinguish one from the other. The second girl warned me that completing the circle would force the structure to choose which of them it recognized as the original.
"What happens to the other one?" I asked.
She didn’t answer.
Nyelle tightened her grip on the railing. "Veyric, I’m your sister. You don’t have to prove that to anyone."
"I know."
"No, you don’t. You see a problem, look for a pattern, and decide that understanding it means you can control it." Her voice trembled, but she continued. "I’m scared too. I don’t know why this place recognizes me or why she looks like me, but don’t make a choice you can’t undo just because you think you have to save me."
Her words struck harder than I expected. I had survived by finding patterns in the creatures, the changing city, and the System’s messages, but this wasn’t a monster with a weakness I could exploit. It was my sister, facing something that wore her face.
I studied the six frames around the platform. Five were dark, while the sixth glowed faintly, and narrow grooves connected each frame to the central stone. If the original chamber had been designed to distinguish two signatures, why were there six frames? Perhaps the structure wasn’t meant to choose between them at all.
I approached the nearest frame without touching the stone. Its markings brightened, and the blue line in my palm stretched toward it.
[STRUCTURE RESPONSE: PARTIAL.]
The second frame remained dark, but the third responded when I moved closer. The fourth did nothing, the fifth flickered, and the sixth brightened more strongly than the others. The pattern was incomplete, but I had a possibility worth testing: perhaps I could redirect the process instead of allowing the structure to force a choice.
I placed my hand against the sixth frame.
The chamber shuddered, and the silver circle around Nyelle broke apart. The bands of light around her ankles vanished as she stumbled forward, while the second girl dropped to her knees, clutching her head as blue light spilled between her fingers.
[SEPARATION CONDITION: ALTERED.]
For one hopeful second, nothing else happened. Then the central stone cracked, and a deep vibration rose from the shaft, throwing me against the railing. All six frames lit simultaneously as the blue line in my palm surged toward the stone.
The second girl screamed. "You weren’t supposed to open it!"
The System’s messages fractured before my eyes.
[ANCIENT STRUCTURE: UNSTABLE.]
[CONTAINMENT FAILURE.]
The stone split down the middle, exposing a cavity filled with darkness. Something moved inside, and a heavy heartbeat rose from beneath the platform, shaking the metal supports.
The second girl lifted her head, her face flickering between Nyelle’s features and a shape outlined in blue light. When she looked at me again, she no longer seemed to be pretending.
"Veyric," she whispered. "That’s where they kept the part of you they couldn’t take away."
Something reached up from the darkness.
It had my face.