“Maybe he lit more than one. At any rate, he picked the poisoned one. He smoked it, tossed the butt from the window; and then the stuff acted.
“He was dead before he reached his apartment.”
BISCAYNE was on his feet.
“Jove!” he exclaimed. “I think you’ve struck it, Cardona! That’s piecing it together. We looked for poison in those cigarettes, and there wasn’t any!
“A cigarette butt — lying on a New York street! Who could discover that? Excellent, Cardona, excellent!”
Then the professor became less enthusiastic. “It will be an impossible job to trace it, Cardona!”
“Professor,” said the detective, “we’re up against some crook who has a big brain.
“I’ve picked up three clews that I think are good. You’ve put the O.K. on two of them. But they are just straws — that’s all.
“Now, I’ll tell you where we’re going to get the real evidence.”
“Where?”