"Aim it at his head and give him the smallest charge the gun is adjustable to, and his most recent knowledge is subtracted from his memory. Give him the full charge, and he is swept back to a childish or infantile age level. The exact age he reaches is dependent on his physical and mental condition at the time he's retroed.
"Theoretically it's possible to kill with the retrogression gun. The person can be taken back to a stage where there's not enough nervous organization to sustain the life process.
"However, life is tenacious. As the lower levels are reached, it takes increasing energy to subtract from anything that's left. Most people who want to get rid of someone are satisfied to leave the victim somewhere between the mental ages of one and four. For practical purposes, the man they knew is dead—or retroed, as they say."
"Then that's what they did to me," said the man. "They retroed me and left me in the Shelter. How long was I there?"
orgenese shrugged. "Who knows? That's what makes it difficult. A day, or two months. A child of two or three can feed himself, and no record is kept since the place is free. Also, it's cleaned automatically."
"I know that now that you mention it," said the man. "It's just that it's hard to remember."
"You see how it is," said the counselor. "We can't check our files against a date when someone disappeared, because we don't know that date except within very broad limits." He tapped his pen on the desk. "Do you object to a question?"
"Go ahead."