at was all; the rider had looked neither to the right nor to the left,
but the word was distinctly uttered. At the same instant an arm dropped
and a long finger pointed to the gleaming white square in the road. It
was like an instantaneous photograph--a flash, and the figure had
vanished in the fog.

"This grows interesting," Steel muttered. "Evidently my shadowy friend
has dropped a book of rules in the road for me. The plot thickens."

It was only a plain white card that lay in the road. A few lines were
typed on the back of it. The words might have been curt, but they were to
the point:--

"Go along the sea front and turn into Brunswick Square. Walk along the
right side of the square until you reach No. 219. You will read the
number over the fanlight. Open the door and it will yield to you; there
is no occasion to knock. The first door inside the hall leads to the
dining-room. Walk into there and wait. Drop this card down the gutter
just opposite you."

David read the directions once or twice carefully. He made a mental note
of 219. After that he dropped the card down the drain-trap nearest at
hand. A little way ahead of him he heard the cycle bell trilling as if in
approval of his action. But David had made up his mind to observe every
rule of the game. Besides, he might be rigidly watched.

The spirit of adventure was growing upon Steel now. He was no longer
holding the solid result before his eyes. He was ready to see the thing
through for its own sake. And as he hurried up North Street, along
Western Road, and finally down Preston Street, he could hear the purring
tinkle of the cycle bell before him. But not once did he catch sight of
the shadowy rider.

All the same his heart was beating a little faster as he turned into
Brunswick Square. All the houses were in pitchy darkness, as they
naturally would be at one o'clock in the morning, so it was only with
great difficulty that Steel could make out a number here and there. As he
walked slowly and hesitatingly along the cycle bell drummed impatiently
ahead of him.

"A hint to me," David muttered. "Stupid that I should have forgotten the
directions to read the number over the fanlight. Also it is logical to
suppose that I am going to find lights at No. 219. All right, my friend;
no need to swear at me with that bell of yours."

He quickened his pace again and finally stopped before one of the big
houses where lights were gleaming from the hall and dining-ro