No stamp. No return address. Just a thick, textured paper with a single line of text:

Leo realized: the license key wasn't for making models. It was for access . Someone had weaponized Rhino 7’s rendering engine to map physical security grids. The key unlocked a backdoor into every camera, every laser grid, every lock in the museum’s subnet.

Then he saw the men. Three of them, in biohazard suits, using a plasma cutter on the case.