Control Tone.

"This one" he shows me a picture of an brain with, like, these lines around it "creates tones, too low for humans to consciously hear, that make anything said within the audible range into commands that the subject will follow without question or hesitation... don't worry that earpiece I gave you will make you immune... Also because people acting in a robotic and emotionless manner are almost useless as infiltration and sleeper agents the tone doesn't make people robots, they simply act as if whatever command they are given was perfectly natural.