"Here's the gimmick. You know about the dope habit. People start hitting heroin or cocaine and can't get off the hook. Well, the same thing happens with poison."
"I don't believe it."
"Some people acquire the poison habit. They eat arsenic for their health and—"
"Their health!"
"That's right. They take it in small doses so it isn't lethal and they build up a tolerance for it."
"Why?"
"They've got an idea it's good for them. For malaria. A tonic. An aphrodisiac. But dig this. Once they start they can't stop. It's habit-forming like dope. They've got to keep on eating poison the rest of their lives."
"I'll be damned."
"And they thrive on it, Jake. That's the truth." I waited a couple of minutes and then asked: "Why'd you throw a fit before?"
He grimaced. "That line about an unknown killer and unknown victims. It was a little too close to home."