Art investigator Madison Dupre knew the offer was too good to be true: $20,000 for a quick trip to Dubai, the fantastic Arabian Nights city on the Persian Gulf. The call came from Sir Henri Lipton, a man who was supposed to be dead-and who she sincerely had hoped was burning in hell because he had ruined her career before his violent "demise."? He told her only one tantalizing thing about the piece of art: "Let's just say it's a couple thousand years...