"What's so odd about that?"

"Nothing," Butters said. "But look, here it is again. There's a fuse marker, and in the third one, poof, it's gone. Your arm is back to normal."

"Maybe I just drink too much milk or something," I said.

Butters snorted. "Harry, look. You're a tough guy. You've been injured a lot." He pulled out my medical file and thumped it down with a grunt of effort. Granted, there are phone books smaller than my hospital file. "And I'm willing to bet you've had plenty of boo-boos you never saw a doctor about."

"Sure," I said.

"You're at least as battered as a professional athlete," Butters said. "I mean, like a hockey player or football player. Maybe as much as some race-car drivers."

"They get battered?" I asked.

"When you go around driving half a ton of steel at a third the speed of sound for a living, you get all kinds of injuries," he said seriously. "Even the crashes that aren't spectacular are pretty vicious on the human body at the speeds they're going. Ever been in a low-speed accident?"

"Yeah. Sore for a week."

"Exactly," Butters said. "Multiply that. These guys and other athletes take a huge beating, right? They develop a mental and physical toughness that lets them ignore a lot of pain and overcome the damage, but the damage gets done to their bodies nonetheless. And it's cumulative. That's why you see football players, boxers, a lot of guys like that all beat to hell by the time they're in their thirties. They regain most of the function after an injury, but the damage is still there, and it adds up bit by bit."

"Again I ask, what's that got to do with me?"

"You aren't cumulative," Butters said.

"Eh?"

"Your body doesn't get you functional again and then leave off," Butters said. "It continues repairing damage until it's gone." He stared at me. "Do you understand how incredibly significant that is?"

"I guess not," I said.

"Harry, that's probably why people age to begin with," he said. "Your body is a big collection of cells, right? Most of them get damaged or wear out and die. Your body replaces them. It's a continual process. But the thing is, every time the body makes a replacement, it's a little less perfect than the one that came before it."

"That copy-of-a-copy thing," I said. "I've heard about that, yeah."

"Right," Butters said. "That's how you're able to heal these injuries. It's why you have the potential to live so long. Your copies are perfect. Or at least a hell of a lot closer to it than most folks."

I blinked. "You're saying I can heal any injury?"