t slowed up and halted at the sidewalk on the far
side.

"Stop in front of a door, Jimmy," directed the detective hastily.

Jimmy obeyed gracefully, and Mr. Birnes stepped out, hardly half a
block behind the closed cab. He went through an elaborate pretense
of paying Jimmy, the while he regarded Mr. Wynne, who had also
alighted and was paying the driver. The small sole-leather grip was
on the ground between his feet as he ransacked his pocketbook. A
settlement was reached, the cabby nodded, touched his horse with his
whip and continued to jog on up Fifth Avenue.

"Now, he didn't order that chap to come back or he wouldn't have paid
him," the detective reasoned. "Therefore he's close to where he is
going."

But Mr. Wynne seemed in no hurry; instead he stood still for a minute
gazing after the retreating vehicle, which fact made it necessary for
Mr. Birnes to start a dispute with Jimmy as to just how much the fare
should be. They played the scene admirably; had Mr. Wynne been
listening he might even have heard part of the vigorous argument.
Whether he listened or not he turned and gazed straight at Mr. Birnes
until, finally, the detective recognized the necessity of getting out
of sight.

With a final explosion he handed a bill to Jimmy and turned to go up
the steps of the house. He had no business there, but he must do
something.

Jimmy turned the cab short and went rattling away down Fifth Avenue
to await orders in the lee of a corner a block or so away. And,
meanwhile, as Mr. Wynne still stood on the corner, Mr. Birnes had to
go on up the steps. But as he placed his foot on the third step he
knew--though he had not looked, apparently, yet he knew--that Mr.
Wynne had raised his hand, and that in that hand was a small white
envelope. And further, he knew that Mr. Wynne was gazing directly
at him.

Now that was odd. Slowly it began to dawn upon the detective that
Mr. Wynne was trying to attract his attention. If he heeded the
signal--evidently it was intended as such--it would be a confession
that he was following Mr. Wynne, and realizing this he took two more
steps up. Mr. Wynne waved the envelope again, after which he folded
it across twice and thrust it into a crevice of a water-plug beside
him. Then he turned east along Sixty-seventh Street and disappeared.

The detective had seen the performance, all of it, and he was
perplexed. It was wholly unprecedented. However, the first thing to
do no