“Thank you, Gordon,” he said, as he faced the servant for an instant.  When he turned again, toward the front hall, the Captain had passed out of view through the front door.

Shirley received a surprise when he reached the pavement on Forty-fourth Street, for Captain Cronin was not in sight.  Two club men descended the steps of the neighboring house.  Others strolled along toward the Avenue, but not a sign of a vehicle of any description could be seen, nor was there anything suspicious in view.  Cronin had disappeared as effectually as though he had taken a passing Zeppelin!

“I’m glad this affair will not bore me,” murmured the criminologist, as he evolved and promptly discarded a dozen vain theories to explain the disappearance of his companion.

Twenty minutes were wasted along the block, as he waited for some sight or sign.  Then he decided to go on up to Van Cleft’s residence.  But, realizing the probability of “shadow” work upon all who came from the door of the club, after the curious message on the wire, Shirley did not propose to expose his hand.  Walking leisurely to the Avenue, he hailed a passing hansom.  He directed the driver to carry him to an address on Central Park West.  His shrewdness was not wasted, for as he stepped into the vehicle, he espied a slinking figure crossing the street diagonally before him, to disappear into the shadow of an adjacent doorway.  This was the house of Reginald Van Der Voor, as Shirley knew.  It was closed because its master, a social acquaintance of the club man’s, was at this time touring the Orient in his steam yacht.  No man should have entered that doorway.  So, as the horse started under the flick of the long whip, Shirley peered unobserved through the glass window at his side.

A big machine swung up behind the hansom, at some unseen hail, and the figure came from the doorway, leaping into the car, as it followed Shirley up the Avenue, a block or so behind.

“It is not always so easy to follow, when the leader knows his chase,” thought Shirley.  “I’m glad I’m only a simple club man.”

The automobile was unmistakably trailing him, as the hansom crossed the Plaza, then sped through the Park drive, to the address he had given his driver.

As Shirley had remembered, this was a large apartment house, in which one of his bachelor friends lived.  He knew the lay of the building well:  next door, with an entrance facing on the side street was another just like it, and of equal height.

“Wait for me, here,” said Shirley.  “I’ll pay you now, but want to go to an address down town in five minutes.”

He gave the driver a bill, then entered and told the elevator man to take him to the ninth floor.

“There’s nobody in, boss,” began the boy.  But Shirley shook his head.

“My friend is expecting me for a little card game, that’s why you think he is out.  Just take me up.”