"Well, it’s a nice design," Menlo offered. "They’re stealth missiles, mostly plastic, and they vaporize in midair in a silent burst dispersion. Their payload is a fog: gelatin-coated microspheres. The psychotropic agent is inside the spheres, and the spheres will only melt in the environment of human lungs. After a few hours in the open air, all the microdust cooks down, and the payload becomes inert. But any human being who’s been breathing in that area will absorb the payload."