It has two entrances, and the one on the side street is not well lighted
at night.

At half-past seven o'clock one evening Nick Carter was standing about
fifty yards from this side door.

The detective had shadowed a man to a house on the side street, and was
waiting for him to come out.

The case was a robbery of no great importance, but Nick had taken it to
oblige a personal friend, who wished to have the business managed
quietly. This affair would not be worth mentioning, except that it led
Nick to one of the most peculiar and interesting criminal puzzles that
he had ever come across in all his varied experience.

While Nick waited for his man he saw a closed carriage stop before the
side door of the restaurant.

Almost immediately a waiter, bare-headed and wearing his white apron,
came hurriedly out of the side door and got into the carriage, which
instantly moved away at a rapid rate.

This incident struck Nick as being very peculiar. The waiter had acted
like a man who was running away.

As he crossed the sidewalk he glanced hastily from side to side, as if
afraid of being seen, and perhaps stopped.

It looked as if the waiter might have robbed one of the restaurant's