“But here’s the thing,” Wolf said. “How that ball was made. How this guard piece functions.” He held it up. “Someone done skipped over the Holy Grail of Assault Weapons. Went to the next level.”

Wolf was smiling now—mostly at Remy, who was holding the trigger assembly.

“’Cause what you got there, girl,” he said, “are pieces to a prototype. You’re holding parts of the first functioning, 3D-printed M24 sniper rifle.”

“We knew that before you walked in,” I said. Grabbing the piece from him.

“Sure,” he said. “But that’s ’cause I’m the one who told Chester. And he told y’all while I was outside.”

I smiled at this. The kid was right.

“Okay, tell me something, Wolf,” I said. “If you had the rest of this rifle and you lost these two pieces, what would you do?”

“That depends,” he said. “If I got the plans and a printer, I’d just make another two pieces. But that ain’t always the case.”

“Why not?” Remy asked.

Wolf explained how 3D printing worked. How architects or engineers designed CAD, or computer-aided design, plans. Sometimes the ones for weapons were published online for free, and 3D printers could use them to make any product. And sometimes they purposely weren’t published online, because of their value.

“You know a federal judge shut down a website last year for putting out handgun designs, right?” Wolf asked.

I nodded. We’d been briefed on this at work. The Liberator was the name of the gun.

Wolf explained how the printing process worked, by a machine printing tiny layers of plastic atop each other, slowly forming the intricate curves and edges of whatever the CAD plan dictated. It could produce a toy. A household object. Even a gun.

“So it’s possible someone can’t replicate the same gun twice?” Remy asked.

“If they don’t own the plans,” Wolf said, “they definitely can’t make the two replacement parts.”

“Or maybe they’re just struggling to replicate it,” Chester said.

“With assault rifles, these guys in Alabama produced four M4A1 carbines,” Wolf said. “But each time some piece broke off on the gun as they took the first shot. Something different on each weapon too. Usually after thirty seconds, they flat-out fell apart.”

“Like literally apart?” Remy asked.

Chester jumped in again. “These are guns made of plastic, Detective Morgan. So like anything that’s machined, there’s tolerances before the plastic gives way. Plus, guys like Wolf paint ’em and sometimes that throws off the tolerance. You gotta shave the pieces down, just to fit ’em together.”

I blinked hearing this. Found the evidence bag in my satchel. The one holding the tiny pieces of paint that I’d found in the trash at the Homewood Suites.

Wolf shook the clear evidence bag, so the tiny filaments separated. He grinned, showing off a metal-capped incisor. “Now you’re getting it, boss,” he said to me. “So if you were making a rifle from 3D-printed parts, you’d print each piece one at a time. Then paint ’em. Then put the pieces together. But sometimes—as cool as it is to have a resin or stain on a piece—it can mess with how the parts fit together. You follow?”