Bourbon Street in the French Quarter of New Orleans probably is the scene of more nightlife per square foot than any other thoroughfare in the world. It was in a joint of the more sordid type that this case began one night. A sharply dressed man in his early thirties had been standing against a wall several feet from a weary piano player observing what went on at the bar. After a half hour or so of this observation he walked across the floor to a door at the back of the club...