"That's what I'm trying to tell you. Why do you always call me your 'dear boy?' You know I'm a year older than you are."
"It's just habit, I suppose. You look so young—your hair is black, while mine is nearly white. You're full of vigor, while I begin to creak with middle age. I didn't realize that I irritated you with my little phrase. I should think you'd be pleased that you have somehow managed to sip at the fountain of youth."
David sank down on a stool. "I'm not pleased. I'm terrified."
"What do you mean?"
"I mean that's exactly what's happened. I have sipped at the fountain of youth. I've discovered how to keep people from growing old. I myself have not aged a bit in the last ten years."
There was a long silence. Karl sat unmoving, his face like stone.
"I don't believe you," he said at last.
"It's no longer a question of belief. In a few days everybody will know, the proof will stare you in the face. And what will happen then?"
"Evidence?" Karl asked. "I can't accept a statement as a fact."
"Would you like to see my mice? Come with me."