ir,
but the gentleman dropped his handkerchief in his chair opposite you."

"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 e