"O.K.," came the amused answer. "No use talking then."
"Just a minute," said Don. "I might as well know what I'm being suspected of. Whom have I murdered?"
"No one, yet. Look, Channing, we're having a time here."
"What kind?"
"Phony money."
"So?"
"Yes. The trouble is that it isn't phony. You can always detect spurious coinage and counterfeit bills by some means or another. We have bits of nita-fluorescin in the bills that is printed into the paper in a pattern which is symbolically keyed to the issue-date, the serial number, and the identifying marks on the face of the bill. It takes a bit of doing to duplicate the whole shooting-match, but we've been getting stuff that we know is phony—but, Channing, having the original and the duplicate here on my desk I can't tell which is which!"
"Give me more."
"I have a hundred dollar bill here—two of them in fact. They are absolutely alike. They are both bona fide, as far as I or my men can tell from very complete analysis, right down to the bits of stuff that gets ground into a bill from much handling. I have coinage the same way. Isn't there something that can be done?"
"We are trying to find a substance that can not be duplicated," explained Channing. "Given time, we will. Until then, I'm helpless."