I wondered what he would think about all this. He’d cracked jokes about my “Little Green Men,” but I knew deep down he was dying to know what it was that GSAF had been covering up. I wished he could see this now.

“We can’t just use Emil’s key to go back,” Nadin said. Her head was bent, rummaging through a second box of supplies that Gitrin had brought from the engineer’s longhouse, and she didn’t look up as she spoke. “Because of what he said about the paradox. His key is the one you and your friends unburied in your time, and what you used to travel back. Its counterpart is with the geroi now. Which means”—she pulled another posternkey, more tarnished than Emil’s but otherwise almost identical—“it has to stay here until we can leave it in the place where you found it. So we’ll copy the coordinates from Emil’s key onto this one.”

Emil moved to poke me again, and I leaned away from him. “Yeah, yeah, I know.” I quickly repeated what Nadin had just said in English.

He nodded thoughtfully. “Does it have a record of the time and place that I left from?”

“It does,” Gitrin answered after I translated. “But it is not exact. The postern that he used recorded a timestamp on the key, so we can estimate the date. But the spatial data will be harder to calculate. The planet is constantly in motion—in its orbit around the sun, and in its own daily rotation. If we had a static connection between two posterns that would make things easier. But those need to be established beforehand—the receiving postern must be programmed to the key’s frequency. Without it, we have to just make a guess. If we calculate wrong, you could rematerialize in the middle of solid rock, or the vacuum of space.”

“So we’re talking potential death here,” I said, frowning.

Gitrin tugged her earlobe. “The safest alternative is to direct the key to transport you to a wide open area, one where there aren’t likely to be many obstructions. Your keys were programmed to bring you to the plateau outside Hope Renewed. I’ll have to program Emil’s key with that information, too, for when you find it in the future—but that will be easier. I know the exact date and time each of you arrived here, and I know the exact spatial coordinates for the plateau on each of those dates. Your time, though, is an unknown to me. How has the planet’s surface been altered? Have there been any changes to the planet’s rotation or solar orbit? Emil’s key gives me a clue, but it’s all just guesswork.”