Late in the night Oct. 16, Rudy Giuliani made a phone call to this reporter. The fact that Giuliani was reaching out wasn't remarkable. He and the reporter had spoken earlier that evening for a story about his ties to a fringe Iranian opposition group. But this call, it would soon become clear, wasn't a typical case of a source following up with a reporter. The call came in at 11:07 p.m. and went to voicemail; the reporter was asleep. The next morning, a message exactly three minutes long was sitting in the reporter's voicemail. In the recording, the words...