oor carefully behind him, and came on down the
corridor, his footsteps echoing loudly on the concrete floor.

At the end of the corridor a second door confronted them. It was opened
by a tall blond man, with a reddish mustache and brilliant blue eyes. "I
heard you coming," he said, nodding to Hartmann, then looked keenly at
Duvall. "So this is the fellow, eh? Where shall we take him?"

The doctor pointed to an iron door which faced that by which they had
entered. Between the two doors ran a narrow corridor, with an iron
staircase to the left, leading upward. "In here," he said, shortly, and
going to the door, opened it with a key which he drew from his pocket.

Again Duvall cursed his stupidity. For a moment, thoughts of resistance
crossed his mind but he at once realized the hopelessness of it, and
followed the doctor into the room. The tall man brought up the rear,
closing the door silently after him.

The room was pitch dark. In a moment, however, Hartmann had pressed an
electric button, and a brilliant light flooded the place. Duvall looked
about him curiously, and in that fleeting glance saw that the room was
without windows of any kind, and that the walls, smooth and white,
contained no openings whatever, except the door by which they had
entered. The floor, as he could tell by its feel under his feet, was of
cement. The room was bare of furniture, but he perceived a number of
boxes and packing cases standing about the walls.

The instant the door was closed, Hartmann sprang at the detective and
grasped his two wrists. The latter had always been considered a powerful
man, but the arms and shoulders of the doctor were those of a Hercules.
"Search him, Mayer," he said, as he pinned Duvall's wrists together in
his iron grip.

The man addressed as Mayer at once began a systematic search of Duvall's
person. With deft fingers he explored his pockets, felt the linings of
his clothing, tore through the contents of his pocketbook. The opera hat
had fallen to the floor, in the short struggle which ensued when the
detective found himself in Hartmann's grasp. Mayer picked it up, glanced
at it carelessly, then threw it angrily into a corner, where it rolled
unobserved, into the shadow of a large box.

"There is nothing here," he said, in a voice of keen disappointment. "He
must have hidden it elsewhere."

"In his room at the hotel, perhaps--his portmanteau," the doctor said,
eagerly, releasing Duvall's hands and throwi