The sadness in his voice made my chest clench. There were no parents on Iamos except the geroi. Ceilos and I had been raised in the households of our biological parents, since we were geroi-born. But all other children were raised by the collective until they were old enough for an apprenticeship. It had always been that way, since the Progression.

“Isaak,” I said, sitting across from him on one of the hospital beds. “I would like to help you, but I can’t do that unless you tell me what happened. Where did you come from? Simos?”

“No, I’m not from Simos,” he said, his expression wary. “I’m from Iamos.”

“You can’t be from Iamos. If you were, you’d know about the System. The System would recognize you.”

“I didn’t say I was from Iamos, I said I was from Iamos,” Isaak snapped.

I jumped up. “What is that supposed to mean?”

He stood as well. “Listen… stop listening with that thing”—he gestured to my earpiece—“and listen with your ears. I am not from Iamos. I am from Mars.”

I stared at him. “But what is Mars?”

Isaak began to pace, running a hand through his dark hair. “The planet I was born on. The fourth planet from the sun.”

“Iamos is the fourth planet from the sun.”

He stopped short. He stared at nothing, at his reflection in the glass. Then, slowly, he said, “What?”

Ceilos pulled his earlobe. “Iamos is the fourth world. Ia, four. Mos, world. Wi, si, ha, ia. Each of the eight planets in the solar system are named this way.”

“The solar system,” he repeated. “Can you show me? On your… System thing?”

I pulled open the visual indicator again and commanded it to display the eight planets. I gestured to the fourth one, cringing at how red the image had become. The blue of the seas had dwindled down to nearly nothing; the green of the ground was a distant memory.

“That’s it,” Isaak said, his voice shaking. “That’s Mars.” He sat down heavily, his shoulders hunched.

I knew it. I knew I recognized the coordinates on the posternkey. It seemed impossible, but I knew I couldn’t be wrong.

Ceilos snapped, “Look, I don’t know what you’re trying to prove by lying—”

“Wait, Ceilos,” I interrupted. I crouched in front of Isaak, looking up into his worry-creased face. “Isaak,” I said. “When you left Mars… did you pass through a door?”

He bobbed his head up and down. “It was an archway made of stone.”

“A postern,” I said. “And you were holding something?”

“Emil called it the key,” he said. “It was metal, ancient. So, so old. But we opened it with a coin.”

I frowned. “I don’t know what a coin is,” I said. “But did it look like this?” I pulled my medallion out from beneath my collar and held it out to him.