“Are the devices that open the door. They fit together, not unlike a memory chip into a deskpad drive. If programmed correctly, theoretically, they can open any coordinates. You could travel from one side of the planet to the other—and potentially between planets as well.”

“The coin fits into the key,” I repeated. “You mean like this?” I unzipped my backpack and pulled out Scylla’s artifact. The recess in the middle was about the right size for the coin to fit inside.

Emil’s breath came out in a hiss. “You did have it!” he snapped.

I put my hands up defensively. “I didn’t know it, though! You wouldn’t stop screaming at me long enough to tell me what the damn thing looked like!”

Emil didn’t answer. He just ran his hands over the key obsessively, scraping at it with his ragged fingernails, holding it up to the fluorescent light.

“How can that be the key, though?” I asked, not expecting a response. “You said my dad had it. This was buried out in the middle of nowhere—” I broke off again in horror. What if Erick was wrong about the skeleton, then? What if it really was—

“This isn’t the same key,” said Emil matter-of-factly.

“What?”

“This is a copy. Look at this marking.” He pointed to the monogram in the corner, the one that so impossibly matched Mama D’s maker mark.

“The other one didn’t have that?”

“No.”

I rubbed my eyes wearily. “So that means there’s more than one.”

Emil nodded brusquely and sat once more. “It makes sense. There were probably several dozen, if not hundreds, of these in production, to allow the Atlanteans the ability to travel freely, to several locations in one day.”

I rolled my eyes. “How do you know they were Atlanteans?”

He glared. “It’s a shorthand, Contreras. How do you know that the city Heinrich Schliemann discovered was actually Troy?”

I ignored him. A sudden thought overwhelmed me. “If this isn’t the same key, then that means my dad still has the other one. Do you think he—” I trailed off. I couldn’t begin to fathom the second half of that sentence.

“I don’t know,” Emil said. “It shouldn’t be able to work without the coin.”

“Unless he found another coin,” I said. “If there’s more than one key, there’s got to be more than one coin.”

“Dear God.” Emil’s voice was gravelly, somber. “Then he could be anywhere. Anywhere in the known universe. He might have wound up back on Earth, but he just as easily could have been transported to Pluto. ”

I gripped the flimsy table so hard my fingers ached. Emil looked at me sympathetically—as sympathetically as someone who looks like an evil version of Albert Einstein could, anyway.