“Another proof of Double Z’s eccentricity,” declared Mann. “I think Cardona was wise to keep it quiet.”

THERE was a short silence while the cab rolled on. Mann realized that the driver was not going directly to the apartment. They were entering Central Park, now. He realized that the man at the wheel must also be in the employ of this stranger in black.

“I have tested your impressions,” came the voice from the corner, “by giving you the simple facts as the police see them. Now let me ask you this: Would Caulkins, as a newspaper reporter, go to that house on East Eightieth Street before he told his city editor that he had received a threat from Double Z?”

“No,” replied Mann thoughtfully.

“Then what about the message?”

“I see!” exclaimed Mann. “It was planted on him!”

“Why?”

“Because — well, because he had mentioned Double Z over the telephone.”

“Now you are getting to the point.” The whispered voice expressed approval. “But why did Double Z allow Caulkins to mention his name over the phone?”

“Probably another eccentricity.”